This post is awesome. I immediately opened a word document and starting writing 2 lists: things that I am already good at and things I want to be good at, I got to about 10 on each. 
Almost immediately, I ran into the question of the definition of "good." For instance, I started running four years ago, I have completed three half marathons and several 10K races. My times are nowhere near good for an avid runner, but for a couch potato they are great. So, am I good at running? More contemplation is needed. 
Also did you see this post at cup of Jo? it is being good at things day on the internets! 
http://joannagoddard.blogspot.com/2012/04/what-are-you-good-at.html