If you pick drinks, limit yourself to 1. And only before the gig. I personally find it rather unprofessional to see a DJ drink while doing his thing (and smoke LOL). But that is just me though.
Being prepared is the best. If you know you have done everything possible to prepare for the gig, it will give you confidence that you are ready to go out and do it. The rest comes with time/experience as you said.
Something else is to accept that things WILL go wrong, no matter how long you have played. Stopping the wrong track, cue-listening to a track with the fader still open, starting a track with the filter still closed, letting the music run out. It ALL happens to everyone at some time or another. If you can accept that fact and let go of perfectionism, but strive for the best possible, you’ll lose a lot of stress too.
As I said in another post. You learn way more from your mistakes than from your successes. So learn to embrace mistakes for the valuable lessons they teach you.