Re: Problem finishing sets, matches
All good advice in the thread, I have taught really strong players who have (to my despair) collapsed in the same way. The same problem can apply at all levels.
I'll repeat the 'one-point at a time' moniker one more time! Or if it helps, just try and zone out and forget points all together. Making first serves will be absolutely huge at this point for your confidence- try some practice sets where you only allow yourself one serve.
Of course, there's no substitute for good old match-practice! Good luck!