In order to correct the energy and rhythm of the walk, trot and canter I pick up the rhythm that the horse gives me and then adjust it... imagine running alongside your horse and then slowing your run down to control his gait.
When the horse is too hard to follow, set the pace without them by moving as though you are riding a quality gait already. In this case, it is better to picture sitting in a swing that has been pushed from below and sideways. The only way to correct the motion is to steady yourself and move purposefully in the direction and tempo that you are looking for (forward and steady).
Remember to carry this over to your tests. When I ride the walk, trot and canter in my tests, I think of every stride as being the energy and tempo that I have chosen.
In the test, remember:
"This is MY trot... this is MY canter. The horse is not the leader, I am."