I've gained an understanding of the motivations behind some of my behavior, and learned to detect and unravel the flattering narratives my brain creates to explain my actions. I've also learned how other people think. As well as being self-knowledge that I want for its own sake, it's helped me a good deal in my interactions with people. Learning about how I and others think has made social interaction a lot easier.
If you are already an atheist that does not believe in ghosts, what can you learn from rationality? I'd love to be wrong about lots of things but my problem is, I think I'm right.
As far as I can tell, none of this reflective thinking has lead to deeper understanding of consciousness. (A subject I wish I wasn't so interested in, because its study seems so futile).
If you feel like it, please tell me about any particular instances where actively working on your own thought processes has lead you to realize you were wrong about something (other than blatantly false things like those I mentioned above) or if the same program lead to any new understanding of consciousness.