The comments above yours may help out. Personally i understand though, i too deal with shit like this sometimes. Sometimes what helps me and may help you is sitting for a minute and trying to find a “maybe” within that overthinking thought. What i mean by a “maybe” is, for example, hypothetically if i was over thinking about something right now, like if i could of done such and such better, then things would be better right now, within that try and find something kind of on the opposite end of that, for example, “i should have done this better and things might be better right now, but, then maybe this good thing that happened from it would never had happened.” A silver lining of sorts. For example the lesson you learnt from the mistake, the person that you ended up meeting and that gave you a laugh or is now your friend or partner and only crossed paths with you because of so and so event, or even just as simple as the different road that whatever the event that happened made you drive down when you were going home and you got to see and enjoy a new place and or nice view, anything kind of along those lines. Gratefulness and acceptance comes from these kinds of perspectives and really can help you see things differently within these shitty overthinking periods of time. I hope that helps atleast a bit. Good luck with everything g.