Depriving an individual of sleep is a psychological technique used by interrogators when trying to break down an enemy and get him to spill his guts. Knowing that, it is easy to understand why sleep deprivation works against you in a powerful way when you're caught in a survival situation.
It's a fact that if you are not able to get enough sleep, your judgement will fail. You'll be unable to make good decisions in a timely manner, and that might lead to your making a bad situation even worse. The stupor that accompanies sleep deprivation leaves you incapable of logical thought. You won't be able to plan your strategy or carry out necessary tasks. For example, too late, you might decide to get a signal fire going … after the search helicopter already passed by and prompted the idea.
But it isn't only judgement that suffers from loss of sleep. Dexterity fails quickly. You might not be able to manipulate the fire starting equipment. Physical strength vanishes, and along with it goes the will to live.
On the other hand, if you are able to get sufficient rest, your mind will remain sharp, reflexes will be quick, and you'll be able to carry out survival tasks. This is why it is so important to make camp early, settle down before the sun sets, get a fire going, eat something, drink plenty of water, and make a comfortable place to sleep. Hunger, dehydration, exhaustion, and miserable conditions all impact your ability to sleep. And while you might think that sleep is a distant priority when compared with shelter, fire, water, food and signaling, they actually all work together to give you the best chance for survival.
Make sure you get adequate rest. Don't work yourself to exhaustion. Guard your energy jealously, and expend only enough to accomplish necessary work. Slow down. Sleep.