I'm still very much a beginner and play at only the lowest stakes but I've had a few such moments of realization.

I've learned to play poker by reading, and reading, and reading as many poker books as I can get. I mean I've read 'em all. The first couple of times I played for money I played at a 1/2 table in a local card room in California. Needless to say, 1/2 players in CA card rooms don't play by the book and being a super tight player in a super loose game just erroded my stack and always led me to get furious over the crazy 'bad beats'. I then played a lot of online poker and live poker elswhere ( 2/4 and 3/6 in AZ) where play is much different. When I returned to the first game i played, I noticed my play was completely different. I finally learned to make all the adjustments I read about and surprise/surprise they worked! Moreover, I saw other players in the game playing the way I used to and having the same lack of success. I realized then I had definitely improved because I not only considered the cards and board, but game conditions, opponents etc. Its funny, you can hear people say "Poker is a game of people played with cards" a million times but when you finally figure it out its a near spiritual moment.