Rhythm and tempo are very important in the downswing. If you find you are mishitting your golf shots and your tempo is too fast, try swinging your club more slowly both on the backswing and the downswing. Your natural rhythm and tempo will return.
It is important to be on plane to maximize your chances of hitting a solid shot. To remain on plane on your downswing, the butt end of the shaft of your club should be pointing at or near the ball. If the shaft is positioned above the correct plane line, your downswing will be too steep resulting in a sliced shot. If the shaft is below the ideal plane spot, the shot will be too flat, resulting in a duck hook to the left or a blocked shot to the right.