There are certain things that we may not perceive very well in the time available.
Great acceleration or decel is a good example of this. On serve often we see a ball
coming from much faster than other shots, giving us less time to perceive the
high rate of decel that takes place on all tennis shots. When we have more time,
we can account for it better and it doesn't matter as much if we don't.
On a fast serve, not accounting for the decel well makes us feel rushed and
hurts our timing...one of the most important aspects for our strokes.
Once you can just realize that the extra time will show up as the ball slows, then you
can relax and have better timing to execute your quality stroke.
IMO this is how "waiting" can help.
Pro Supex Big Ace