Many players, without realizing, make up their mind too soon as to where they are going to meet the ball, rather than tracking the ball’s flight all the way into the hitting zone.

It may be imperceptible at first how much the ball speed is diminishing, but if you do the following drill it will help you realize how long YOU CAN wait to make up your mind.

Place yourself at a 10 ft. distance from the net. Have a friend on the other side, about 3 ft. from the net, feed you (underhanded) slow pace, medium height balls to your forehand. After a few balls so he can gage his toss to where you can hit it comfortably, close your eyes before the feed.
Your friend tosses the ball as before, without crowding you with the toss, and exactly when the balls bounces he’ll ask you to open your eyes. Find the ball while tracking it and moving as necessary and then hit it comfortably at a medium pace with a real good finish of your stroke, usually over your opposite shoulder.

Don’t rush. You’ll find out that you have more time than originally, when you prepared the shot.

Why is that? It is because a medium paced ball slows down considerably during and after the bounce, both because of the ball’s friction with the ground and the air resistance. It has been measured in professional tennis that from baseline to baseline the ball loses approximately 60% of the speed, while serves lose about 55% of the speed. A 50 mile an hour groundstroke becomes a 20 mile an hour in your vicinity, a 100 mile an hour serve a 45 mile an hour floater when it gets to you.

Waiting for the right moment to strike lets you adjust with just one reaction, that one decided on real occurrences and present time. Preparing early you’ll have an approximation which you’ll need to correct at a later time. In effect, you’ll have to change your original decision and are doing things twice.
Or, even worse, you’ll correct your swing as you are already swinging towards the ball.

View it this way: the mind is slow and also stubborn. It sticks to decisions; you may be forcing the action rather than staying calm, looking at what is happening totally in present time, and responding accordingly.

Give the above drill a try and you may find it a lot easier than it sounds.