I believe it's possible to understand anything. However, the human mind is one of the most complex systems out there. The only thing more complex I've found is sociology/politics... 'cause then you're not dealing with one mind, but billions, all operating simultaneously. Sociology is one of my current perseverations.
When I say I've got myself figured out, I mean that I have an operating knowledge of my motivations, desires, and goals. All that is subject to change in the future. I also probably shouldn't have said totally figured out, because yes it is a mindfuck, in a way.
However I'm a firm believer in the idea that just because a thing is understood, doesn't make it any less valuable or worthwhile. That's a common and annoying fallacy that I ran into a lot, especially at art school and among religious types - the idea that if it can be scientifically explained, if it can be "reduced" to materialism, it's no longer special. The idea that god is god because of his/her/its unknowability, because it's totally beyond human comprehension, ever. Or the idea that it's not real art, it's just craft, unless it comes straight out of someone's Freudian unconscious. The problem with that was that with many of these so-called artworks, I could explain them, I could see how to mimic them well enough to pass an art equivalent of the Turing test, and I could trace them back to mental motivations on the part of the artist that demonstrated values which deserved only scorn when brought into the open.
Claiming one cannot understand one's own unconscious is generally (not always though!) born of laziness or ignorance of psychology. However I believe it's possible to mathematically prove that a contained system can never fully understand itself. I don't know the proof offhand, but I could probably track it down if anyone gave a damn.