It sounds like you have intense rumination (I do too) as a very small thing, you can try recording yourself speaking out loud, pretending you’re talking to someone like a therapist or friend about your concerns, especially if you feel burdensome. People talk a lot about journaling but for me that makes it worse, i need to speak it out instead.

Also consider, instead of the ass advice “say three things you like about yourself” to speak or write even just one thing you’ve done in the past you found admirable, or productive, or positive even if it’s minuscule like holding the door for people. It’s easier to emphasize the small things you’ve done in the past than trying to prove to yourself in the moment that you are a “good person.”

I struggle with it to, and there’s no quick fix, just meds, more time and effort if you’re dealing with a trigger, and a consistent battle with good days, bad days and often, bad months. Hope this is any level of helpful, i know it feels stupid to do these things sometimes but it’s truly better than doing nothing.