Usually when writing some code, which deals with something new for me, I get many "idiot questions" in my head. I try to write comments in a way, which will answer my future self's "idiot questions". Answering all those questions, I feel more like I truly understand, what I am doing.
I often don't comment code, especially in personal stuff, but when I occasionally do, which happens mostly when things get overwhelming, I find bugs or fix things that I was stuck on. Writing forces you to understand better, name better, and almost feels like providing you with another perspective, all without leaving your own self.
