Tennis is a lifetime game as it needs millions repetitions to be successful.
Here are some reminders leading to high performance:

• Don't aim for technical perfection. If it's good enough it's good enough
• Go last mile with extra session to work the serve
• Play more training matches or count points to replicate tournament condition
• Sprint sessions instead of running "marathons". You already run on the court
• Target legs and abs off the court
• Constantly research the game strategy and tactics
• Eat anti-inflammatory diet and drink clean
• Every training must contribute to turn good habit into unconscious competence
• If different players report the same issue in your game then seriously think about it