The greatest change in my personality for the better happened during my freshman year in college. This was also the time when I was a successful lucid dreamer, and I don't think that was a coincidence: lucid dreaming caused me to become more self aware, and thus I discovered that my personality had to change, and it did. I think this does not have to be limited to lucid dreaming, dream self-interpretation could also cause personality change I think. Mostly when our consciousness and subconscious start working together, I think that can lead to powerful self improvement after becoming more aware.