The arguments about practice, and family, and money, and health in smokey rooms, etc, don't affect a teenager for the most part. Most of us diehards, no matter what level we ended up at, spent all of our waking teen hours in a pool hall, gambling our brains out, motivated to the highest level to best our peers. Yet, after 5 to 10 years in the same room, amongst the same players, some turned out to be open players, some stayed at a high C, and some were inbetween. My opinion is that boils down to natural ability.
Sh!t, I played softball for 10 years in a local neighborhood league. Everyone was accepted, no need to try out. I went to every game, had the same coaches, went to all the practices, felt the pressure, same as every other kid. I went every year from grade school age where we played T-ball, to I think 16 when they cut off the age limit. Amongst the 100 or so kids in this league, some were good, some sucked, some were in the middle. Again, my opinion is its natural ability. Especially when looking at kids with sports... they don't have any distractions, and all want to be a baseball star some day.