There is no living being that does not need to sleep or rest completely every day.
If you want to know why, remember how you feel when you do not sleep one night or when you only one night go to bed later than usual! The next day you’re so tired that you cannot function properly. While we sleep, our body cells are recovering from work during the previous day and build up energy reserves for the next period of activity.
How much sleep do we need? For most people it is enough to sleep a few hours. However, some people have even less sleeping hours, while the others need more than eight hours to sleep.
Largely it depends on the lifestyle. The old rule, which can be observed, is that we need to sleep as much as we need to be able and eager to work.
There are deep and easy sleep. After eight hours of light sleep we still feel tired, while our short but deep sleep can completely refresh us.
Normally, when we go to bed, our brains sleep same as our bodies. Sometimes it’s just brain sleeping and the body does not. Therefore, very tired soldier may sometimes sleep, and to continue to walk in the column, because his body sleeps.