If you are serious about making gains you will get to a point where you have to push past fatigue or muscle failure. If muscle building is your thing, sure you can continue to build muscle and with that make reasonable strength gains but you will get to that sticking point where you need to draw from the depths of your capacity, where having that mental edge that comes from sobriety will help you make that PB. Personally I cant draw for the animal if im thinking beautiful thoughts, I have to be thinking a bout that pussy who did me a wrong! (Not to mention the danger of lifting heavy weights whilst under the influence).