When hurricane Milton hit I lost power, internet and my cell signal was like using dial up so all online access was gone for about a week. Sent the family to go stay with friends and I stayed behind. With no electricity and no internet all I had was myself. The first 2 or 3 days were tough. I didn't know what to do with myself so I cleaned and sat outside in the shade to escape the heat. By the end of the week I was in a good place, not perfect, but better than when I started. I was relaxed, my thoughts were clearer, I could comfortably focus on one thing at a time. I think knowing that after I was done focusing on something I could return to a comfortable quiet helped.
When power and internet came back within 2 days everything was back to 'normal'. No more peace. No more comfortable focusing. Back to my usual habits. I recommend disconnecting from phones and computers for a few weeks. Give your mind time to get into the habit of not using them, it's so easy to fall back into old habits, you have to set the stage for new ones to slowly grow, like trending a garden it takes time and effort.
One of best descriptions of self mental health care was from Rick and Morty. It's like wiping your ass, or washing the dishes. It's not fun but it's something you have to do everyday. You can suffer the pain of doing it, or suffer the pain of having not done it. Front load the pain don't offload it to your future self. Give future self a break, do some work for him/her and I know they'll be incredibly appreciative.
I'm my past when I was at my worst I noticed that I was in a better place when I was around people than when I wasn't. Be around people/friends if you can. Ask someone to spend party of a day with you doing absolutely anything.
Exercise until you know you will be sore the next day. I didn't exercise regularly, but I did notice that whenever I did some physical activity that left me sore the next day, within about 2 or 3 days I was a much better version of myself for a day or two.
So in conclusion. Do nice things for future self, even talk out loud to yourself about future you like they're someone else. Disconnect from Internet and tv so your mind can have some time to itself. Be around people, we are social animals, we need to feel like we are part of a group, a tribe, maybe go take some night classes that will force you to work on a project with others. Exercise or do something strenuous.
Oh and a couple more things, try to establish a regular sleep schedule! Someone mentioned this already and they're right, change your environment. Your mind and body will default to the feelings it's used to having in the place it most often has them. As an example, if you're a home pooper then when you get home your body will go into pooping mode. If you only use your bed to sleep and not look at your phone or watch tv then you will feel sleepy when you get in bed. New environments will put your mind into learning mode not default mode, keep finding ways to keep it from sitting back down into the depression it's left in the chair. Like that song, you can get used to a certain kind of sadness.
Okay one more thing, video games. I like playing them but I have a habit of using them like a drug. It feels good to use a drug, and when you hardly feel good why wouldn't you use it. You will play them again, and you'll enjoy them more after your mind has had some quite time to itself. You'll get to play again someday, you just have some mental chores that need tending to first.
Last thing I promise. Quite time is even better when done in nature. Any nature. Hundreds of thousands of years of evolution designed us to be in nature, part of nature. Quite time means no podcasts or music as well.
Now get out there and do the dishes, wipe your ass, and do something nice for future self, they fucking deserve it.