I sleep whenever I am tired. This keeps me well rested and immune from sickness. Sometimes your body needs more sleep than other times, depending on various factors in your life. Maybe you're under a lot of stress. Or, perhaps your body is weakened, because it is attempting to fight off sickness. Sleep and regenerate. Otherwise, your body will lose that fight with sickness and you will be run down and sick, at which point you'll probably go to the doctor's office or hospital and since your immune is compromised, you'll catch something far worse and die!