Temper your transition
Breaking 70
Speed is great in the golf swing except at the transition from backswing to downswing. Get too quick at the top and you`ll tend to throw the clubhead away from you body and come over the top, which costs you power.
One way to get a feel for a good transition is to think of the top of the backswing as a school zone, then push the accelerator as you come out of it, and floor it to the highway speed.