"Our wretched species is so made that those who walk on the well-trodden path always throw stones at those who are showing a new road" (Voltaire)
This quote about conformity says a lot about who we are as a species and it's a good one to remember when you're trying to develop yourself as a tennis player. In the teenage years, you will have to deal with a lot of pressures from your peers and it will be almost impossible to resist. You must, however, be different than your peers if you are to succeed at tennis.
In many ways, tennis players are really very different from other athletes and, more importantly, non-athletes. Our sport requires both skill and athleticism. Furthermore, you are very isolated when you are on the court since it's usually just you and the opponent. I would say that tennis players and boxers have to deal with similar psychological obstacles except that in tennis there is no corner-person to guide you through the next round. Therefore, you need to learn to think for yourself and, in this regard, you need to become your own best friend. Unfortunately, a lot of tennis players become influenced by negative persons in their lives. People tend to be jealous of the amount of travel that you do, the coverage that you get in the local newspaper, the school announcements outlining your achievements as well as the attention that you get from the opposite sex. Many will try to drag you down in order to make themselves feel better about their own inadequacies. You will often hear how you're following a silly dream and how uncool you are for not "hanging out" or for foregoing the prom to play a tennis tournament. Resist these naysayers will all your energy!
If you care about tennis, I strongly recommend surrounding yourself with positive influences - be it athletes, artists or scholars. Positive attitudes (just like negative ones) feed off, and build upon, themselves. If people feel that they have something to lose, they will tend to make better decisions in the course of their lives. There is nothing more tragic than having someone dictate your dreams for you or, through their actions or attitudes, destroy your dreams. Figure out what you want to do with your life and focus your time and energy on making sure that "you're firing on all pistons" when it counts.