 Sorry for my broken English, but please help me, give me some advices, tks!!!

I know a guy. He is a pretty famous stylist. He can pick a fight with anyone, even a strange in the bus, random guys on stress and a lot of online arguments on facebook? No matter he won or lose the fight, how angry he is when fighting, Just 1 hour late or longest is 1 day late, he seem fine like nothing happend. Feel like he just forgot all about these fight and negative things then go hangout with me. HOW??? 2 weeks ago i got in some stupid fight with a employee of a coffee shop because her attitude with customers is rude and lately some dumb arguments on internet. It already 2 weeks and I can't get it out of my mind. I just feeling angry, upset about some people i don't even know or even met their face and probably never meet again. Why i can't just forget all about it like him? I think he can be famous and have a success career like that because he won't let's some stupid and negative thinking drop him down like me. We know each other but not that close to ask him to give me advices. I have try find something to do, keep me busy, but in the night i will keep thinking about it. I have try deeply thinking about these fight like: why she so mean to me? Maybe she had upset something before or for some reasons make she behave like that. I should let's it go because maybe she doesn't really meant it or it's just the way how she talk...etc. Please give me some advices, how can you forgot or get over your past fight? How you can deal with it? Or if you not, am I the only one that get bother by dumb dumb things, normal people do not like that?

I have depression and social anxiety disorder too. I'm trying to have a life and a career like a normal person because i don't want to be a disappointment for my family. But I know if I keep always upset and thinking about the fight in the past, i will never get better.

Thank you for reading until here. Sorry for my broken English again. I use google translate alot, so if i not reply your comment yet, please forgive me, i have to google translate what you said and what I reply to you, maybe it will take a litlle long times. But pls know that I appreciated any think you said, thank you!!!!!