I agree with Andy V! Make sure you can hear everything, including your bass drum. I used to get fatigued easily when I was playing in a country band that did 4-45 minute sets with 15 minute breaks. If I can hear my bd clearly, I don't overplay. I also went to in-ear monitors which helped as well. I take a Super B Complex and Potassium vitamin every day, plus a multivitamin. I have found that if I'm eating right and getting enough rest, I play a lot better. That includes not having to drive a long way on the day of the gig (me doing the driving and not just riding). On the 2 nighters, I always played better if we stayed in town overnight & I got plenty of rest.
I played this weekend filling in with a country band, and I had no problems. I could hear the bass drum and everything else very well. Get plenty of exercise and protein in your diet.
Good luck!
Mike
