In martial arts there tends to be a dangerous trend among practitioners that is cutting there power in half. There accuracy and speed are lessened by half also. What could cause such drastic changes?

In most arts, there tends to be the training of the one side. Picking either a right hand or left hand lead, the practitioners only work their dominant side. Bruce said let your strong side go forward to greet the opponent, but he never said forget the rear.

Being able to throw good accurate combinations with power and accuracy and speed means you must train both sides equally. If you use your right punch niety percent of the time, when you throw the left you'll look like a pitcher on a baseball mound. Telegraphed and sloppy. Often even if there is speed and power its negated because the shot misses or glances the target. Not to mention that variety in attack and stance should be a good part of your training as well. You should be able to flow from right to left side lead while combo-ing smoothly and without telegraph. Your weak side front should be so strong, fast, and accurate that it appears to be the strong side to your opponent. Until you put the strong side on him. This is the way boxers and Wing Chun practices. These are the best hand techniques and they are pert of JKD curriculum. Also it helps to be able to kick well with both feet as it will help your kicking and your footwork. To be able to attack and defend from all angles you must have equality on each side of the body. Drill, Drill,Drill.