Relationships suck sometimes

Why do couples fight so much? Why do we all find a need to or a way to be mad with the one we love? A lot of times It could be a trust issue, it could be a jealousy issue, or it could even be that one of you doesn’t feel you talk enough. I don’t get why these things cause fights in relationships. I know me and my girlfriend and I have these exact fights and actually had 2 of the 3 fights I mentioned last night. I talked to her about what I am going to be putting in my apartment next year and she freaked out. I told her about the pong table I am going to make over the summer and how legit it was and so her response was, “sounds pretty official, this means you’re going to be drinking all the time huh?” if u can’t tell, she doesn’t like that I drink and especially doesn’t like that I do it while she isn’t around. I honestly don’t want to change for her though. I am having fun being who I am. And the way I look at it was she did the same shit to me last year when were dating. She would go out clubbing all the time without me and not even try to invite me. So I got mad and told her I didn’t like it. You know how she responded to me? Well she simply said, “I am sorry. This is what my friends and I do and we are going to do it.” So that’s how I feel about this. She can either embrace it, or she can let it drive something between us. That’s what I had to do. Sorry, this blog kind of just turned into a rant. Anyway, I don’t understand why couples have to fight about such dumb things? Why not just support who the person is and if they do something that could hurt them, then you step in but otherwise let them be them. You chose them to be with for them. Why would you try to change them?