Too afraid to close your eyes? Afraid that you might drift off and lose track of time and reality?
Many psychologists, while explaining away the accounts of people who claim they have been abducted by aliens, say that those individuals are victims of sleep paralysis. Sleep paralysis is a physical condition which allows the body of a dreamer to be immobilized while dreaming thereby preventing the individual from acting out their dreams and perhaps getting injured or killed. If you are dreaming that you are jumping from your fourth story window to fly to France it is evolutionarily advantageous that you are in a state of sleep paralysis, no argument there.
But is sleep paralysis more than that? Does it have another function? Are you really afraid, of being abducted? Again?