Ezra has an interesting post on a book he read and "the fundamental inaccessibility of another person's mental life," by which he roughly means (read the post yourself for a better explanation) that despite spending years trying you won't understand why someone else behaves the way that they do. This ties in with something i was just talking about a moment ago, which is that i've begun to doubt that most people have a reason for what they do before they do it. That is most reasons are just tacked on retroactively and thus change depending on what's happened since then. In the case of this book, of course she cannot understand why he killed himself, he himself would have only had a reason retroactively, and if he killed himself then he never had a chance to have a reason to have done it. I still don't apply this theory to everyone, but for a lot of people a lot of the time this seems to be the case.