My friends got upset with me after I didn't go out with them because I didn't know what to wear. (Yes, that's an actual reason..) But they were/are so ***? Just because I didn't go out? It's not the first nor last time they left without me, so what's the problem now? What bothers me the most is that instead of just "complaining" our argument turned into them literally cursing at me (Fu*k off, eat *** ect.) We were meant to go out in a big city. I am very insecure about my looks, so if I don't make sure that I look "good" I will feel very uncomfortable and my anxiety will come out.
So I need an advice: How do I make up to them?
You say "they left without me"...does that mean they got impatient and just left? If that's the case, it's not something they can blame you for. Do they know you feel you need to feel just right before going out? Have you talked to them about this? You should. As it stands/sounds, I don't think you need to apologise for anything. Them cursing you is certainly unacceptable.