There's a reason why pressure causes tennis players to struggle. Typically a player who is feeling pressure does the cardinal sin in tennis: grip their racquet too tight. In other words, tension increases in their body. This creates choppy swings and inconsistent results. We all have experienced this before and if you pay close attention, I'm willing to bet you feel it without any pressure while you play. This is because it is so common for players to do this at all levels. The best thing about working with this issue in your swing is that it will help reduce the risk of injury. The tighter you are, the less mobile you become so trying to swing hard with a lot of tension will increase your chances of injury. So read on to try to help not only your game but your chances of playing this sport for years to come!
#1 Tip To Loosening Your Grip: Awareness
I do not say "relax" to my players anymore. They will just get more tense trying to relax! That is obviously not what I want to happen so instead I try something else. When I see a player tightening up, I get them to be self aware. Try this, as you are reading this, fixate on your mouth. Is it clenched? How about your shoulders? You immediately start relaxing those specific body parts as you become aware of how tight they are. That is my best advice for you when you play. Practice feeling the tension in all parts of your body to see what needs to be lessoned to allow a more free swing.
Here's the video that can give you more of a visual for what this all means.