Nightmares are manifested by scary and devastating dreams. In severe cases, they are associated with sleep disorders, heart problems, permanent fatigue, high levels of anxiety, fear of falling asleep, or secondary cognitive deficits after sleep deprivation, and thus may increase vulnerability to the development of other mental disorders. Lucid dreaming, the dreaming experience, and the realization that one is dreaming are easy-to-learn techniques that can provide effective and significant relief.