Not checking in with someone if we made plans. My wife will ask if I texted my family to see if we're still doing the thing we planned. If I make plans with someone, then I'm going unless they tell me is cancelled. My family could make plans for 12 years from now and we'd all be there a little earlier than the time we said we would be there.
When people often text me or call to make sure plans are still on, it has the weird effect of making me no longer want to go. I'm introverted, but if I make plans I will be there. So it sort of opens the door for me to cancel for some reason.
I noticed certain people will either change the time or day (or forget the confirmed time, or that they already initially set a time and seem to randomly change to what works for them without updating others and accuse like everyone else had the wrong time) or cancel without telling others. So those people I check to see if it’s still on and reconfirm the time even up to an hour before the meet up.
I usually give up on a person who does that as it’s emotionally exhausting to constantly coordinate around a changing target. I get enough of that at my job.
In the case of my wife's family, if we make plans, most of them are guaranteed to show up late. We've made it a habit to plan things for 30 minutes to an hour before we actually want to start because we know they'll be late. Being a veteran, it drives me crazy. If I'm not a few minutes early, I feel like I'm late.