When people are active, they usually don't feel sleepy. When they take a break from activity, or feel bored, they may notice that they are sleepy. Adults who don't get enough good sleep feel sleepy when they're bored. Boredom, like a warm or dark room, doesn't cause sleepiness, it merely unmasks it. Resting in bed with your eyes closed cannot satisfy your body's need for sleep.
Sleep is as necessary to health as food and water, and rest is no substitute for sleep.
As noted above, sleep is an active process needed for health and alertness. When you don't get the sleep you need, your body builds up a sleep debt. If you drive when you're sleepy, you place yourself and others at risk because drowsy drivers can fall asleep at the wheel with little or no warning. Find out here. Snoring is not harmful as long as it doesn't disturb others or wake you up.