You are feeling bad about it so you are obviously not a crappy friend, but you may need some organizational help, for remembering events, and a way to motivate yourself on the day of. I do struggle with these things. I have found having and using a calendar app (I use Calendars by Readdle because it color codes and putting in events is super easy, and I can see all my events at the month view and it just looks pretty) really really helps. If I rely on my memory, I’m screwed. Looking at my calendar every morning is a great habit (you can also set it to remind you of things coming up) and so the forgetting part is a lot better now. But the motivation to do social things, well you’re seeing the consequences of not actually going. You may have to remind yourself when the time comes, that you have to put in the face time in order to maintain friendships. Explaining your struggles to your friends (I don’t think they have written you off but you might owe them explanation/ apologies, this is not elementary school where friendship is over as soon as you do something wrong) explaining, not to have to excuses, but so that they understand how your brain works, and maybe letting them know that in future you’ll have a plan for keeping appointments, I think might help