I don't know if this is a "right" or a "wrong" answer, but in my particular case for an incident that happened, I know that the more I thought about it, I kept playing things over in my mind. The more I did that, I kept thinking of things I might have done to prevent it. I just tend to blame myself for things anyway, so I eventually started to blame myself, and who knows, maybe it really was my fault? Deep deep down, I don't think it ultimately was my fault, but it is hard to find that place.

I hope this helps, and welcome to PC. Good question!