This situation happens to all of us more often than we would care to admit. A common mistake made in an effort to correct the problem, is to simply take a hold of the reins to slow the horse down. The problem with this solution is that the horse will just speed up again as soon as the rider lets go of the reins. Additionally, the horse is likely to become more and more non-responsive to the bridle. The first part of the solution is to think of the problem in a different way.
Horses are pattern animals.
They behave in patterns and they pick up on patterns of stimulus quite easily. One of the easiest patterns for horses to learn is that they can take away our ability to control them by rushing, or trying to get ahead of us. They quickly learn from experience that when they rush, or try to do things faster than the rider wants, the rider will usually back off and quit pushing on them. What the rider does next is to pull back on the horse's mouth. You would think that this would be more irritating to a horse than being pushed.