Most of us are aware of the importance of sleep. We may not know why, but we know that when we don't get a full nights rest; we usually don't feel our best the next day. The amount of sleep needed varies from person to person. Some need 8+ hours of sleep, while others can get away with as little as 7 or less.
So why should we get enough sleep instead of living by the phrase, "I'll sleep when I'm dead"? Well, for the most important reason, a lack of sleep over a long period of time may actually shorten your lifespan. Therefore, that "sleep" that you're putting off, may come sooner as planned - and not the good kind of sleep.
Sleep correlates with memory, body function, overall health, and even your mood. your mood is one of the first things to be affected. In fact, your mood might even be impacted before the lack of sleep has even happened. Let's say you're up past your bedtime and you like a certain amount of sleep. Now, you're anxiously counting the hours of sleep you'll get if you go to bed at "this time". Sometimes the anxiety knowing you won't get the sleep you need keeps you up even longer. So by now, your mood is already affected due to just being aware that you won't get the amount of sleep you prefer. You may wake up feeling exhausted or irritated; regretting staying up past your bedtime. Which is not the best way to start your day.
Overtime, a lack of sleep will start to impact your overall mood and health on a daily bases; even if it feels like you've adjusted this new lifestyle. The little tasks now become a burden and it may be easier to just not deal with them. Enjoyable activities may lose their value, simply because you don't have the extra energy to share. This can lead into a more serious problem, such as depression and/or anxiety. Which this may turn into a more serious problem if it is not taken care of right away. Taking care of yourself means getting the sleep your body needs. A healthy, rested mind, is a fundamental for having a happy mind.