In order to rest, a person must stop anything he is doing that is work intensive and give his brain a break from concentrated activity. Resting doesn't necessarily mean sleep; it can be achieved by stopping to read a book or play a game for several minutes or longer.
Rest can also be attained by taking a short nap in order to recharge. This is not the kind of nap that takes 2 or 3 hours, but is instead a power nap of 15 or 20 minutes to rejuvenate the mind and body. The important things is to take oneself out of the realm of normal activity for a short amount of time, engaging in something that is enjoyable and relaxing.