I had the luck to understand this very early (being 17 years old).
I've gone to math and physics competitions, and while I had good results I could see that there are the top level guys who are above my level: there is no point in directly competing with them. So I thought I should do something different and I became a programmer.
Nowadays I also see this in programming. There are markets where competition amongst smart people is too high. Too much smart people want to work for the most famous companies, too much smart people create programming languages and frameworks, too much smart people want to start their indie game studios, too much extremely smart people wanted to win the Netflix prize... While I love these topics, so I sometimes compete in these very competitive markets, I know that it is/(would be) wiser to do someting different where competition/(expected value) ratio is not so high.
