the source of the problem

I am utterly exhausted. Living like this is draining the life out of me; it’s so exhausting. And then there’s the fact that random strangers treat you badly—even when you haven’t done anything—and you have no idea why.

You don't understand what’s going on or what happened. You can't figure out what’s wrong. If I could just find out what I did wrong, maybe I could identify the problem.