When we don’t have a routine, or we stay awake the whole night every now and then, we disconcert our body as it works with the circadian clock and tries to balance our sleep/wake needs.
Let’s say that a boy has the following situation: It’s 8:00 am on a school day, and he has not been able to sleep for 23 hours (for whatever reason). His circadian clock is telling him that he should be awake and ready to work at school because it is the morning, the sun is out, he should be at school and it is time to be awake, sharp and ready to learn. However, he has been awake for 23 hours already, situation that pushes him (internally, through sleepiness) to go to sleep.
If he stays home and decides to sleep it is likely he will have trouble falling asleep, both systems (the circadian clock and his internal drive for sleep equilibrium) are working against each other… it is not known if he will actually fall asleep at that time or not.
In this case, the boy will not get a good sleep, he has accumulated sleep debt plus he has varied his routine.
In order to best satisfy our drive for sleep is to get the sleep we need in a regular schedule, that is to sleep enough at the same time frame every day. This routine, when we don’t deviate from it too much, will work towards getting good sleep.
When we go against our sleep needs, and we accumulate sleep debt by staying up for long periods of time, and we intend to sleep against the natural force of our circadian clock which drives our sleep/wake rhythm, it becomes harder to fall asleep and be awake when we want to. Therefore we can get good sleep when we stay in our daily routine, and we change it as little as possible.
The natural question now is how many hours do we need to sleep? What is the minimum sleep we need to function right? What are the consequences of not sleeping enough?