It’s tough. Try to remember that you are not your thoughts. The brain is just doing what the physical brain does, think. Just like the heart beats. You’re not your thoughts. I know easier said than done. Sending hugs and peace.
One way of thinking that I’ve found helpful specifically when dealing with the concept of uncertainty is my philosophy of 99.9% sure-that is I’m 99.9% certain that all of these thoughts are junk, they’re not me or reflective of who I am, and I can safely ignore them and go on with my day. You’re right that you can’t be 100% certain, but then again you can’t be certain that the world won’t end tomorrow. Accepting uncertainty is just about accepting the fact that there isn’t 100% certainty about anything, which is a state you’re already in. It doesn’t mean you’re any more likely to do any of the things flying in your brain, it just means that they scare you a lot and so inherently prove your goodness. Trust and believe in that, not the fear. :) Give the .1% to the universe and go for a nice walk.