Top advice right here. The “Give Mozart a toy piano and he’d write a concerto” principle. The PA is an instrument…play it!
Also, I cannot underscore enough the earlier advice to have some kind of backup: mp3 player, iPhone…some device independently able to produce an entire set’s worth of music if your main rig fails.
In their days of performing on laptops with Max/MSP, Autechre carried around a Minidisc player full of tiny snippet tracks and would put it on auto-shuffle if the laptop crashed.