I have learned that my son responds positively when I work to remediate his drive to excell in sports (now Football and Baseball). Somebody said earlier, I really liked it, that it is hard to put a grown adults head on a kid's body. I'm afraid that if I don't slow him down and try to make him aware that life has many other things to offer all he would do is study, play his playstation, lift weights, train and practice.
Somebody else wrote about not neglecting the soul. I think that this is very good advice for teens and young adults. My son is 15, not all that interested in driving or girls. I think that this is because he has heard, many times for many years, adults and coaches say things like "oh! He was a great ball player but when he turned 16 he became just another kid with a car." or, "Once he discovered girls he lost interest in playing ball." It would be nice to see him socialize outside of sports with his friends. Lots of kids call the house for him to go to parties or dances but, he just isn't interested.
Time off is essential for my son to "recover" mentally from competition. He is very intense and feels driven constantly to be better than everybody else to the point where I get concerned about his psychological development. He seems to tolerate 90 games per year physically a lot better than he does mentally. From being an adult and observing many kids as a dad around highly competitive baseball for the last 6 years I think that I have seen a lot more mental "injuries" than physical ones. I can tell when my son needs the break at the end of the season when frustration starts taking over. It starts to get hard for him to "just let it go" when things don't go his way. It seems to me that this happens to kids when perspective has gotten out of whack in their life from being wrapped up for to long in the game without a break.
I vote for downtime as being necessary for their development as people and ballplayers. After taking time off, some of the "bad habits" that have developed over the year magically disappear when he gets back to it. (On the other hand my son is not a pitcher (thank you God), he plays MIF and CF and has a pretty good bat.)