Insomnia is a common sleep disorder that can make falling or staying asleep hard. Patients with insomnia usually complain about difficulty falling asleep and staying asleep. It also can cause you to wake up too early and not be able to get back to sleep. You may still feel tired when you wake up. Insomnia can drain your energy level and affect your mood. It also can affect your health, work performance, and quality of life. How much sleep is enough varies from person to person. But most adults need 7 to 9 hours a night.