Have you ever, given someone a major step up in life, been a mentor, and measurably altered the trajectory of their life for the better?

One of my best friends in elementary school was a son of Turkish immigrants.
His parents didn't speak any German, so naturally he had serious issues with the language, too.
This held him back in school, which lead to him getting sent to the lowest tier of secondary school.
(We have 3 tiers in Germany. The highest one (Gymnasium) qualifies you for university, the middle one (Realschule) used to qualify you for highly-skilled work that doesn't require university, and the lowest one (Hauptschule) for the trades. Nowadays, even trades jobs scoff at the middle tier, and the lowest tier is basically a direct route to a life of shit jobs or unemployment.)
But just by hanging out with him as a friend, I taught him German, how to use and fix computers, showed him the world of books, and connected him to German society better. I'm not trying to brag, he was a very bright kid and it wasn't like I was doing this as welfare, he was just a good friend and we shared what we liked with each other.

25 years later we met again by accident. He actually recognized me when he saw me on the street in a different city.
By then he had switched from Hauptschule to Realschule, went on to get his qualification for university, studied economics, created his own company in the IT sector, and had 6 employees. And he told me that my friendship was what kept him out of the wrong circles. On the old computer I had given him (which my parents had replaced) he had taught himself how to use office programs, so he was the only one in the family who could do the taxes, which taught him about finances.
At the time I met him again I was actually unemployed and working odd manual labor jobs under the table, after failing my university education twice due to depression.
He connected me to some contacts he had, which landed me an IT support job, and now I have a pretty good career as a sysadmin.

I met a girl in art school and lost track of her for a few years. During the pandemic we found each other again. He was trans now, identified as a male and had massive anxiety and body-image related problems.

It was so bad, that he stayed at home for weeks, only ordered food and basic needs online and got an instant panic attack when leaving the house.

I dragged him out to various events and spent time with him as much as possible for almost two years. It helped him get back on his feet.

As soon as he was able to handle his life without my help again and met another guy, he ghosted me.

That hurt a lot, but I would do it again. I still remember visiting him one day and he just started cutting into his arm in front of me because of his mental issues, it was really brutal. I would've felt like an absolute asshole if I left right then and there, even if the outcome wasn't positive for me in the end.

I hope he's doing well now and maybe one day realizes that he shouldn't have treated me the way he did. I don't want gratitude, but an apology would be nice.

Gave some advice to a female coworker of mine who was a few years younger than me (we worked in a restaurant and were 25 and 18 or smth). She was in love with her housemate and wasn't sure if it was mutual, afraid of losing the friendship, a classic. Talked for a while and it was pretty clear to me from what I heard that it was mutual. Talked her into taking the lead and they've been together for years now.

When I first started my career, I was in a new town and looking for friends. I met this guy, and we started hanging out. It was cool, we had a lot in common and spent many days playing video games together and hanging out at the local stores. He told me his anxiety was so bad that he dropped out of high school, didn’t have any other friends, was still living with his parents, and couldn’t really hold down a job. We had some deep conversations about these things, trying to work through the whys and things he could do to get over them. One day, he told me that he really appreciated our friendship, and that it helped him get over some of his anxiety and basically feel worthy as a person. He eventually started hanging out with other people too, and even got a girlfriend. Eventually, he went on to get his GED (turns out it was easy, he just didn’t have the confidence to try), is going to community college, moved out of his parents, and has a job he enjoys in his field of study already. I moved away, and we don’t talk as much as we used to, but last I heard he was doing great. I don’t feel like I did much, just hanging out with a friend, but I’m glad I was a part of getting his life moving in the right direction.

Not sure how deeply positive it was necessarily, but as far as I can tell I changed at least one person's life significantly.

When I was in middle school I learned how to solve the Rubik's cube through online tutorials, and afterwards I was basically addicted to it for a while and I was messing with a cube all the time. One of my classmates was interested in learning how to solve one, so I drew a bunch of guides and taught him the terminology, and soon enough he was also hooked on the Rubik's cube.

I eventually grew tired of it, but he kept going and learned how to solve all sorts of smaller and bigger cubes and pyramids. I bumped into him at uni a few years later and he had a cube in his hand lol. Last I heard of him he was even participating in some local competitions, but idk what he's up to now.

Even if he ultimately gave up on his speedcubing dreams I can at least say that I introduced him to a cool new hobby that kept him entertained for several years.

Convinced a long distance friend to change their major from Acupuncture to Computer Science before they ruined their life.

They're doing better than I am, now.

I mentoured some jr devs and some apprentices. You end up learning quite a bit about yourself, your industry, and your straighths and weaknesses pretty quickly doing so. Telling someone, "well that just what worked" is not good enough.

A few times I've been there for friends and helped them through rough times just by being someone to talk to.

But I also helped my best friend and roommate by paying most of the bills while he developed his IT/engineering skills. He's got a good career now but struggled for a few years.

Then I took someone in a couple months ago and she's staying in my attic now. That's going well, my wife and I get along great with her. Hopefully it'll all turn out well.

I've done this a few times through my life, especially lately as I've finally been getting my own life stabilized. Here's some more "notable" examples.

A family member, where I've been trying to mentor them and help them in every way I possibly can - sometimes at great personal cost - but as the saying goes, I've led them to water but I can't make them drink. Still won't give up, though.

Another family member I've done the same for has actually been trying to take me up on it. Still early stages, but they've started on applying for college in a field they're interested in. I'm helping them study since it happens to be adjacent to my own field, and I'll help cover the bulk of the cost if they don't qualify for gov't funding. I'm really hoping things work out for them.

The only time I've really actually seen obvious results is in my students where I volunteer teaching English. One student in particular really struggled to read even a single word, but in less than a year, they can now read most sentences on their own - which is honestly just insane to me.
Obviously it's like 99.999% their effort rather than mine, but I like to think I'm helping lol.

...writing this all out makes me feel like I'm bragging or something. Really I've just been in a rough spot for most of my life, and now that I'm getting my life together I'm just trying to give back a bit where I can. I just want everyone to be happy, lol.

At my last job I got several thank you notes from people who were leaving for better positions. They credited my coaching them with their success. Most were pretty sharp on their own so I'm not so sure I contributed all that much but it was nice that they thought of me.

Not in a way that I've really followed up on after, but bringing up the next 'class' in the sense of giving the new folks those tricks that are not in the books and letting them take over where you left off happens a lot in my work. I suspect people do so more than they know every day though. Sometimes all it takes is to sell someone on the idea that they can do the thing that they're not so sure of.

I do know I've been on the receiving end of it though.

Yes, and then he ghosted me...

I don't think one could consider me as ever having been a mentor in the sense one is looking for, but someone I remained friendly with despite her being an outcast among everyone else made me happy when she implied I gave her hope that someone could be proud of her, her finishing by saying "and that resonates more than even some questionable romantic companion might". She says she thinks of me whenever dealing with anything, "like an internal Jesus".

Every day

Yep.

Countless people. Well, maybe thousands. Almost nobody ever helped me back, grew beyond me. Why? Because I suffer from so much childhood trauma, stress, I never realised it until last year. Only now am I working my own machinery and getting my house in order. The friends I helped get out of rut, left me in the rut. I was always a broken machine fixing others altruistically. Fixing privacy community since the past 5 years, and what do I get? Death threats, abuse, trolling, witch hunting, ignorance... as I disregarded myself for the greater good.

Society has taught me that Buddha was correct in saying prioritising oneself is not selfish. Society will never help you. It is the very rare handful people that do. It is infinitely worse when you are a cis man. People come crawling to help a woman or child or minority. Men must care about themselves just like other groups do.