Focus on What You Can Control
Do you worry about your competition, the weather or course conditions? This is a waste of energy and focus. You can't do anything about these things. There's only one thing that you can control, yourself. Focus on your confidence, physiology, positivity and behavior. In essence, it is all about you.
Fretting over outcomes will also take your focus away from what you can control. If you take care of the process, the outcome will take care of itself.
If you find yourself worrying about the end result, try this process-focused method of scoring: for each hole mark if you gave yourself a shot at birdie (or par depending on your level of play) and if you 2 putted the green (or better.)
This will keep you from stressing over the final outcome. If you had 2 checkmarks for each hole on this scorecard, your outcome would likely be great and your focus would be outstanding.