The magic of astral travel.
When you astral travel your supposed to be connected to your physical body by this silver thread (not a physical thing but the connection may as well be physical) that cannot be severed. If anything goes wrong on your astral journey you are shot back into your body. Often if you become afraid this is a one way ticket back into your body. Astral travel is very different from lucid dreaming in that their are things outside your control in this other plane such as other astral travelers and beings that live in the astral plane with free will as well.