I just read an “expert” stating that the quality of your tennis depends on what is inside your head.
I disagree. It’s outside of your head!
Style is muscle memory. If you learned the mechanics correctly you’ll do the same most of the time, adjusted by your instinct. So this first part is physical, simple, easy, especially if you learned tennis the modern way.
Who controls your disposition? Again, you, yourself. You are you, not your brains or your head.
Timing is spiritual as well. You are playing a game, you have the tools, you take your time, you perform the usual way.
Feel is even more spiritual. The mind does not feel. It may record it.
Instinct is even higher. It is a computation that uses all of the above.
It may be necessary here to say that tennis is easy to perform, provided the tenets contained within our teachings are followed in full, which those who find it difficult would gain to learn.