Tennis is made up of different parts. When having a bad game of tennis, figure out which part is causing you to play badly and rethink that piece. The four pieces of tennis that affect the game are:
How you hit the ball, your shots, your stroke production. It’s the skeleton, the basis of your game.
It is made up of whether you are a defensive or offensive player, whether you go to the net or stay on the base line, or whether or not you hit crosscourt.
Physical is made up of footwork, balance, power, recovery, endurance, and speed.
The mental portion is all about concentration, motivation, staying in present, and control of emotions.
If you’ve had a bad game it could be one of those four parts. If you’re technically having problems you could have a lesson. If you’re tactically having problems try thinking about what you’re doing differently and try to work out how you can work out a new tactic plan. Mentally, the best way is to play a lot of matches. You learn how to handle concentration and control of emotions by practicing.