I guess you could say the biggest thing was Deviantart happened. I joined DA near the end of 2011 due to the encouragement of some online friends. I did a lot of art in 2011 on another site, and some of my other artist friends there told me about DA and I decided to join. I had thought I was already pretty good at the time (silly me), but seeing all of the amazing artists here made me realize just how out of my depth I really was.
It sort of opened my eyes to what was really possible in the art field and is probably the final catalyst in my decision to pursue art professionally. 2012 was sort of my "gotta kick things into high gear and catch up" year. I studied lots of the tutorials offered on DA and it's probably been one of the greatest contributors to my overall improvement.