When you begin to gain it is an experience that you want to feel in every portion of your life. If you feel unhealthy or tired/hung-over, you're going to have less motivation to get the most out of your workout for the days you will be. Personally when I really notice my gains its a time I'm at my most physcally fit. There are days I probably would have skipped workouts had I not concentrated on getting an entire routine that made my whole life healthier. Smoking and drinking are just about ok in moderation, but what about like when you want to lose
weight? You can't just eat whatever you want so I think if you really want to make gains you would do it better keeping it on the lighter side. Honestly cigarettes and alcohol have really damaging side-effects in the long-run over time, the best thing is to understand why it is you like those 2 habits then really focus on if there are better ways you could be spending your money and talents.