When playing your instrument-
Focus more on how you sound versus whether it's "right" or not. A better sounding note is usually only a half step or button away from a wrong sounding note.
Practice
Consistent practice is very important! Spending 5 to 10 minutes a day of focused practice is much more effective in learning than practicing 30 to 60 minutes once or twice a week. Having the daily repitition will help you learn quicker and enjoy the process of becoming a better musician!
Performing
Try to play through mistakes- they will come off less like mistakes if you don't freeze up and stop.