A nightmare is a bad dream, that dreamers might have a several feelings while he is having a nightmare such as fear, anxiety, upset, guilt, sadness or depression. It's so natural to have nightmares between time to time, almost everybody experience nightmares  and majority of people start to have it  since they were kids in age of four to eight , In old times people were believing that nightmares are works of demons , they thought the demon sits on the chests of sleepers and cause them bad dreams. There are two broad types of sleep: REM () and NREM () sleep ,most of our dreams occurs at REM phase and we usually remember them more easily if we awake in REM period, what happens that sometimes the dream we have during REM period is scary dream ,so we end up in morning waking up with fear or anxiety because of the bad dream we had which is "nightmare". There are different causes for nightmares it might be pressure, problems or stressful situation happen to us during day time and effect on our dreams, or it could be illness causing a nightmare like fever or certain type of medicine or drugs, there are other causes like death of loved one or horrible accident sometimes changes in life can be a resulting a nightmare, like changing job, lover  or house.
There are certain steps might help you to avoid nightmares and enjoy having more peaceful dreams:

1. Avoid eating direct before bedtime.


2. Avoid having heavy exercise before bedtime.


3. Try to sleep and get up at same time everyday and avoid having naps during your day.


4. Have a clean, relax and peaceful bedroom atmosphere, it would help you to feel more peace and secure.


5. Take the most comfortable sleeping position when you attend to sleep.


6. You may listen to quite music while you are sleeping.


7. Some people feel more comfortable and secure when they keep the door open or use nightlights.


8. Avoid watching scary movies or read scary story books, right before sleeping if you think it might effect in your dreams.

 
Beside these tips, there is a technique that can help you to avoid repeated nightmares ,it calls "facing your nightmare" to use this technique you need to remember or write down the recent nightmare you had that upset you .Track  your dream till the point that you feel it start to turn a nightmare , when you reached to that point ,try redesign and use your creativity to imagine the same scenario but you be the hero this time and facing the fear that you had in your nightmare ,let your self feel empowered ,strong with lot of confident try to have a happy ending were you be the controller and hero. And tonight before going to sleep ,sit on comfortable position try to remember your pervious nightmare like watching a movie but instead of reviewing the sad ending ,remember the scene you created earlier before ,try to feel being powerful in dream and enjoy being hero of your dream. That would help you to be more relax tonight when you will sleep and also would help you next time when you have a nightmare to face your nightmare and the fear while you are dreaming.
 
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