This is a very simple ritual, easy for everyone to perform. It should work for people who have repeating nightmares (children as well ; a friend of mine reported it helped him with insomnia, though)

You need:

• one white candle (not big)
• one white or silver ribbon (it should be long enough to fit your wrist)
• any piece of silver/ an object made of silver that you don't constantly wear on yourself and sleep with it (it can be a ring you don't wear, or a silver cup, even a silver spoon)

Sit in the dark in your bedroom, put the ribbon around the candle, light the candle and put it some place opposite to your face. Watch the flame burning for couple of minutes and relax... then close your eyes and imagine beautiful scenes... which are, in your mind, related to emotions of happiness and peace. It could be anything, it's quite an individual thing. Meditate for as long as you wish... When you feel relaxed and able to focus on one single thing, approach the window, holding the burning candle in your hands, and look at the Moon. If you can't see it from your window, or any other window at your place, or from the yard, just keep on standing there and then just look at the Sky. Say these words:

The Moon is my friend
who's listening to me
bringing the beauty
into my dreams.
The stars are here
forever to shine,
bringing serenity
and peace of mind.
When I close my eyes
they won't be gone,
keeping me safe
till the dawn.

You can repeat these words for as many times you want, if you feel you need to.

After this, extinguish the flame, in case the candle haven't burned down, take off the ribbon and put it around your wrist before going to bed. Leave the candle and a piece of silver on your window till the next morning. Then remove both of them, and the silver ribbon from your wrist. You can repeat this ritual 1-3 times a week, always using a new candle and a new ribbon. However, collect the ribbons. When you feel your nightmares are gone and you got rid of them, you can still go doing this little ritual once a week. It can be done on any night of the week.