I've come to the realization that I'm a negative person, how can I change this before I push people away?

My girlfriend and I were talking late one night (only been together a few months) and she let it slip that her brother thinks I am "easily annoyed by things." Which I find odd because I am especially toned down and pleasant around her family (raised in a southern family that values manners).

After a short debate, she said that it makes me seem like a negative or pretentious person. This really bothers me because the more I think about it, I realize that she's right and I've always been this way.

I am a standup comic and the main reason I do comedy is because I get on stage and rant about certain things that bother me. Whether it's reasonable or not, either of them work. But this way of thinking has been in my life long before comedy, and really as long as I can remember. Even at age 13 or so.

I constantly want to point out flaws in things to make a joke or because I would LIKE them to be changed. But it doesn't actually bother me... If that makes sense. It's more of just my way of starting conversation or telling a joke. In hindsight I can see how toxic this is.

I hold very high standards for myself that are not possible of accomplishing, and maybe I apply this thinking to other people. Perhaps it's a deep rooted insecurity, however I'm very confident and happy with who I am as a person.