Count To 5 

A good practice on groundstrokes is to wait for the bounce, and start counting.  One through the bounce, 2, 3, 4, and 5 through the stroke.

You’ll notice eventually that you need to pause before the five.  There is much more time that you would think.

Between this type of timing and reinforcing the finish lies the secret of many of the top pros, whether they know it consciously or not.