a phenomenon of out-of-body experience - phenomenon of floating outside of one's body, and in some cases, perceiving one's physical body from a place outside one's body (autoscopy)

to have an out-of-body experience

body / physique, constitution, frame / health

even if one says

experience (an experience or one's (overall) experience)

to experience

exit, secession

leave, secede, quit

dark / netherworld / hidden / confine, imprison

he / distal demonstrative, something far off removed from both speaker and listener: that / boyfriend