I can only speak for myself. I tend to compete against the person or persons. Instead of playing against the course. As far as the mental aspect. I now try to concentrate on my game and beating the course. Oh ya, Beta Blockers help as well. They keep your heart rate and blood pressure down lol!!
Professional Athletes use relaxation techniques.
There are about 12 or so to choose from.
I use 4 different ones because sometimes one can fail (learn them one at a time).
They are on the internet everywhere-read up. Pick one, or more.
Just like your game...you have to practice with your new relaxation system.
Pressure my brother...pressure.Its the same reaction most people get when a cop pulls up behind them. Even if you havent done anything you feel suspect. Its that mental mind !@#$that will always garner higher scores. Wax on...you know the rest.