Finally one thing that no one in their right mind can complain about with training. You need sleep. Lots of it. For most people 5 hours a night isn't going to be enough, most of us can do pretty well on 7-8 hours a night, some people need 8+. If you wake up feeling crappy every morning, with your muscles feeling weak and you feeling foggy-headed, you either need to tone down the drinking, or you're not getting enough sleep.
Sleep is so overlooked. We're all guilty of it not getting enough at one point or another. There's a finite amount of time in the day and by the time you finish work, class or rehearsal at you don't want to go straight to bed, you want to relax, see friends, watch movies, do things you enjoy. Far too often that means sacrificing a good few hours sleep. Once in a while is fine, but it shouldn't be a regular habit.
Sleep is necessary for muscle recovery and muscle growth. Hard rehearsals? Sleep. Tough training session? Sleep. Suddenly discovered your new piece relies almost solely on upper body strength and you haven't managed a pull-up since college? Sleep.
Your muscles heal themselves when you sleep; physical adaptations occur during the recovery period meaning recovery is the most important part of your training. Lack of sleep = lack of recovery = lack of progress.
Lack of sleep increases your cortisol levels during waking hours. At normal levels cortisol, a hormone that breaks down body tissue, is necessary in the body. However elevated cortisol levels contribute to muscle wastage, decreased bone formation and suppress the immune system. Increased cortisol levels compromise your body's ability to heal muscle tissue after strenuous work. Levels are further increased due to stress, so if you're stressed and not sleeping, your body is really going to be struggling to recover.
Looking to maintain or improve your body composition? Adequate sleep is needed for fat loss. Numerous studies (a couple of which can be read here, here, here or here) have shown that sleep-deprivation has an adverse affect on fat loss, regardless of diet or exercise routine. On top of that, sleep deprivation leads to an increase in levels of ghrelin in the body, a hormone that triggers hunger. Fatigue often tricks your body into thinking it's energy levels are too low, so an increase in appetite is often associated with sleep deprivation.
Dancers with hectic schedules, even more so for freelance dancers, will often get by on less than optimal amounts. If you're performing into the night, bar-tending to make rent, up early to teach or to go to class yourself, it can be difficult to schedule yourself a regular sleep pattern. Just because it's difficult doesn't mean you shouldn't do it. If you want your body to recover, you want your strength to improve and you want to control your body composition it's as important, if not more so, than your physical training and your diet.