Control problems, especially throwing high, are usually the result of stride and release point. Webball.com and pitchingprofessor.com break down good mechancis visually, with good explanations of how they work. Good luck
Try being more aggressive with your legs. If your legs move slowly, there won't be enough power to the arms and your release will be high. Accelerate your legs and your lower body towards the catcher's glove and it will help the arm speed. Without seeing you throw, this is something to experiment with.
Another good exercise is to play catch with someone at a distance of about 100 feet. Half way between you and your partner, drop a hat on the ground. Throw full speed like you are pitching and try and hit the hat. Pay attention to making adjustments with your body. If you miss high, how can you adjust your throw lower. You will be coaching yourself to better control.
Alternatively, pitch with your eyes. What I mean is don't think of what your body is doing just see the target, see the line of the ball going where you want, and make it happen. If it's still high, try and bounce the ball to the catcher.