Simple thing I try to remember is that I can't control everything, so concentrate on where I can make a difference.
By that I mean allowing time to find the venue, parking, setting up, and making sure that my gear/leads/mic etc is all working properly. (I've spent far too many sound checks watching other band members searching for the elusive 'dodgy lead' somewhere all the chain putting a spanner in the works.)
At least then when the gig starts, you know all your stuff ain't gonna let you down.
In short, there are enough things beyond your control at a gig (audience, venue, other band members etc) but at least your end of things is watertight!
Oh yes, and relax and enjoy the gig! Not everyone gets to do it, so just chill and go with it! Good luck.