Originally Posted by PhrygianDominant
I believe it's mental, but how do you fix this?
a lot of it is mental but physical side has huge influence on mental. you definitely need to make your fh much better technically so your mental side won't start doubting your fh capability during a match. it's confidence issue on your fh by yourself. also try to make your fh more versatile. try to hit flat, topspin, short and big backswing, on the rise, low and high contact point, etc. when you have firm idea how to execute your fh for all the different situations you'll have more confidence in your fh.