Sleep is just as or more important than your nutrition and training. 

Here are the following reasons you want to ensure you have your sleep dialed in as much as your diet and exercise selection.

Weight Gain

What's the point of training hard if we're going to stab ourselves with lack of sleep? Studies have shown that lacking sleep (less than 7-8 hours) in as little time as a week amplifies weight gain. Your glucose tolerance is impaired as glucose levels rise to a level similar to that of a pre-diabetic. In a normal scenario the food you eat, mainly carbohydrates, will be broken down into glucose and you subsequently release insulin. We uptake the glucose and carry it over to your muscles and store it for energy use. In the sleep deprived state, this utopia is blemished and you start having floating glucose. Floating glucose= floating in the pool aka more fat gain. This same mechanism makes us more susceptible to cardiovascular disease and diabetes.

Performance

No sleep, performance lacks. Your reaction time, ability to recall events, and overall brain function begins to decline. Often times we do not  notice this down-regulation of brain function since we compensate and think we are doing fine when in actuality we aren't. How does this translate to training or sport? If you're in practice or a game such as basketball, football, track, or any other sport that require you make reactions, your ability to make those reactions slow down. You will not come into the gym and move incredible heavy loads since this takes mental drive to complete taxing activities.

Compromised Immune System

When we lack sleep, our immune system is becomes less reactive to outside pathogens. We live in world where there are all types of microscopic bacteria and pathogens just waiting to get inside of us and cause those lovely flu's we love to have. Our bodies, when well rested are more than equipped to fight these outside influences. No sleep? We become walking bait for sickness. 

Impaired Recovery

Exercise and life breaks down nearly all the systems in our body. During sleep, we release hormones (growth hormone and testosterone) that rebuilds what we have broken down throughout the day. We also hardwire new movement patterns to have better learning and perform them for the next bout of training. When we skimp on sleep, our ability to recover from exercise and learn new movement patterns become impaired and defeats the purpose of training.

Impaired Sexiness

Upon waking, men should wake up and be ready to knock over buildings. In other words, when sleep is lacking your libido dips. Testosterone levels drop and you begin to lose muscular gains alongside flag raising capabilities. Women's interest begins to drop as well.

To Conclude

Sleep is astronomically important to not only being an awesome human being, but having the capability to perform and recover in the gym. Program your sleep just like you dial in your macros, volume, and intensity of your training. It is absolutely imperative. You will love yourself for it.