Trusting your shot... walking across a balance beam a foot high is no problem right?
Raise the beam 50 ft in the air and you'll start trembling and second guessing yourself because now there's a serious consequence for failing. Remember that pressure is just an illusion.
What's the worst that can happen if you lose a tennis match..?
The consequences only have as much significance as you give it.
So when players are having trouble translating their level of play from practice to a pressure situation, they need to remember it's the same balance beam. Hit or miss... you've got to trust your shot.