Juggling the soccer ball will help improve your timing and body control: When you juggle the ball, you have to correctly time your touch to keep the ball in the air, and continue to take good touches. You have to balance your body, and control the ball and your body in space to keep taking good touches.  Thus the better you can juggle the soccer ball, the better your touch on the ball.  The better your touch, the better you will dribble, pass, receive passes, and shoot and thus be a better soccer player.  Get out there and juggle.