Nightmare
Nightmares can appear for many different reasons. A nightmare tends to be extremely vivid dream that evokes feelings of helplessness, terror, anxiety and sorrow. They can be linked with anxiety, depression, sleep disorders as well as post-traumatic stress disorder (PTSD). New studies have found out that nightmares actually help prepare us for real like traumatic scenarios. While others believe that nightmares can predict bad events to happen in the future.