Lots of children do have nightmares and struggle to cope. They might have sleep problems and are worried and anxious. There are lots of ways to help and one very helpful way is to help the child change their dream in some way to make it less scary.
The child is encouraged to write down their dreams and scale them from 0-10. Then to order those dreams into the ones with the strongest feelings and weakest feelings. Work can then begin on looking at that dream in more detail and changing something about it.
There are tips on how to sleep better and a few relaxation exercises to try.