My response to people messing with me is usually "stop it 
you're being dumb!", however my roommate and best friend asked me to stop saying that to her because she had a really toxic friend in the past who'd tell her she was actually stupid for really small things, and she's reminded of that. 

I've never ever meant to make anyone feel dumb when I've expressed myself like that, I use it as an alternative to shut up, but I understood immediately that it was hurtful to her and I'm trying to be conscious of what I say so I'll never hurt her again. I've never noticed how much of a habit it is for me to use it when I'm teased, and we tease each other a lot and when we're rambling it sometimes almost slips out but I manage to stop it. I feel terrible for reminding her if her toxic friend.

But today I slipped up without noticing, because she was texting some guy from my phone and I wasn't mad but I got really embarrassed and riled up, so I tried to take my phone from her while saying all kinds of shit but we were both laughing and stuff. Afterwards, I asked her how she was doing, just to be friendly, while we were getting ready for bed, and she said in a nonchalant tone (at first I thought she was gonna tell a joke) "oh I'm just hurt because I've asked you not to call me dumb but you did anyway". I immediately apologized and told her I wasn't even aware and that I didn't mean to, to which she replied yeah. I asked if it was when she used my phone, (I wanted to know so I can prevent it in the future) and she said yes, it was, and I apologized again.

I feel like such an asshole, and my mind immediately went "you should leave you don't deserve her" and lots of small flaws seem to be huge now that I'm an asshole. Like anything good about me is rendered obsolete because I made her feel bad. But if I left it would be selfish of me because I'd just be trying to make myself feel better by running from my problems and she's blame herself so I really am selfish and I get stuck in these loops where I can't do anything because it'll be wrong but existing is also wrong.

But at the same time I also want to defend myself, and I can't wrap my head around whether that's right or wrong. I know I wronged her and made her feel bad, and that this isn't about me, but the way she talked to me made feel like I did it on purpose? Like I purposely hurt her which is unfair because she was provoking me to a point where I had no idea what came out of my mouth, and it's obviously not her fault, but I don't think it's really mine either. I've been really aware of myself and trying to change for her and it just feels like she completely disregarded that, and didn't aknowledge that my apology was sincere that I feel so fucking bad. But I also feel like I don't have the right to tell her that, since I hurt her. And I don't want to make this about me, I don't want to be toxic to her but my head is going around in circles and I can't sleep and I want to cry I love her.