Insomnia is a common sleep disorder that can make it hard to fall asleep, or hard to stay asleep, explains Dr. S. Naik (Homeopathy). You may still feel tired when you wake up. Insomnia can sap not only your energy level and mood but also your health, work performance, and quality of life. How much sleep is enough varies from person to person, but most adults need seven to eight hours a night. At some point, many adults experience short-term (acute) insomnia, which lasts for days or weeks. It's usually the result of stress or a traumatic event. But some people have long-term (chronic) insomnia that lasts for a month or more.