Somewhere behind the athlete you've become and the hours of practice and the coaches who pushed you is a girl who fell in love with the game and never looked back. Play for her. -Mia Hamm.
This is one of my favorite quotes as well. The fact that it comes from Mia Hamm is even more appropriate, given all that she achieved in her sport ... soccer. Without the basic love for the game you had as a little girl, the activity (be it softball, soccer, playing an instrument or whatever) becomes more like a job than the fun it is meant to be. When this happens, it is time to give up that which you used to love or refind those things that made you fall in love to begin with and set aside those things that are obstructing that love.
In anything you do in life, always keep that youthful exuberance!