Yoga Course 235. Dream Yoga. Cognition in sleep. Some people sleep a lot, some sleep little, some say they sleep 4 hours a day and are full of energy, and some say they sleep 12 hours a day and are just as full of energy - and vice versa . Some people dream, and others say that they never dream of anything. The ability to sleep is very important for recovery and spiritual development. If you don't sleep for a little while, the person becomes nervous, but then nature takes over and the person switches off. In yoga, sleep is used for the internal development of a person, acquiring abilities and beyond abilities, intellectual and spiritual power, knowledge of the universe, and solving many life problems.