[header] How to fall asleep again after a nightmare [title] Relax your body. [step] In most cases, a person will wake up suddenly because of a nightmare. This sudden shock to your system from fear can cause your heart rate to rise. 
By tensing and relaxing your muscles, you may be able to return your heart rate to a normal level and easily drift back to sleep. [substeps] Tightly tense and release muscle groups by beginning at your toes and ending with your forehead.