The thing is some people just have the passion and motivation to do something to a further extent. In the case of pro-gamers they have reached a point where their passion for "x" game has given them the top skill and mastery to play it at a high level. If you look at the stories of some pro gamers and how they came to be a lot of them were really smart and talented kids who were going to go on to further education (seems like most out of high school going to Ivy League/Prestigious Universities), but instead they devoted themselves to that one game cause they enjoyed it so much and made a career out of it.
Personally I wouldn't be a progamer (I'd probably coach tho). Progamers tend to be very docile during the day, have streaming requirements for sponsors, lots of traveling internationally and lot of other factors to consider. So honestly does your personality and work ethic match what it takes to be in this job.