Practicing countless hours a day as a tennis player without purpose is like struggling in quicksand.
Effort used -> Effort wasted
Always make sure that your players have 1 clear purpose in every practice.
After the practice help them evaluate how well they did on the specific purpose.
1 way to help them is by asking them them to decide how well they did on a scale from 1-10
No matter what they answer ask them:
1) Why it isn’t the number below or the number above.
2) Challenge them on what they need to do better in order to reach a higher number closer to 10
3) Then reinforce their answers at last by saying: “So when you know that you need to do x better in order to get to i.g. 9 on the 10 scale when you are practice your court positioning, what will you do next time you practice your court positioning?”