Why Do We Have Nightmare?
I have my own theories on this. We can all agree that mind is a very wild thing. To put it at ease will be a very difficult task. Sometimes the nightmare we had just doesn't make any sense. We are not sleeping in fear but still the nightmare comes.
I believe people had nightmare because they sleep not because they wanted to sleep but they forced themselves to sleep. "Tomorrow I need to work, I must sleep, MUST". The mind is very wild at the time so no wonder it reacted with the nightmare. Somehow people from previous generation know about this. That's why they relate having nightmare to not washing your feet. Scientifically, why do we ever need to wash our feet before we sleep?
1) to clean it up so that our bed will be clean? - possible
2) to cool it off so the comfort will help us sleep? = possible
I choose to believe that washing your feet is a cooling down session for your mind. The action itself is telling the mind (in the most persuasive way) that you wanted to sleep. Then with all the "doa" you recite, the mind will immediately prepare to go to sleep mode. And lastly we recite the "kalimah syahadah" which is supposed to be the last word we utter for the day before we sleep. This will subconciously tell the mind "Good night and sweet dream" :)
--------------- Personal Note --------------------------
When I was a kid, my nightmare almost always involved two beast (usually elephants) running toward each other with me in the middle of the head on collision. Very short but at the time very scary hehe. Usually it is a sign that I will be down with fever the next day. Do you have any reoccuring nightmare.