ie.: The idea was "(blank)". It didn't come from myself, it was divine inspiration, dumb luck, etc.
or maybe: My essence/spirit was outside my body. It was "(blank)".
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Sign up to join this communityie.: The idea was "(blank)". It didn't come from myself, it was divine inspiration, dumb luck, etc.
or maybe: My essence/spirit was outside my body. It was "(blank)".
In regard to the second part, if you truly felt your spirit had left your body, there is a set phrase for this: out-of-body experience.
People who have near-death experiences (another set phrase) often report out-of-body sensations as a part of the experience.
People who are able to intentionally induce an out-of-body experience, wherein they "travel" to other places, are practicing what is sometimes called astral projection.
See also remote viewing which has been a recurrent topic discussed by Art Bell on his radio show Coast to Coast am. Here is one such episode:
ecstasis or ekstasis: to be or stand outside oneself, a removal to elsewhere from ek- "out" and stasis "a stand" a form of ecstasy
The word for something that arises outside oneself but affects or becomes parts of oneself is "exogenous." This seems to fit with the "The idea was" part of the question.
"External" merely means on the exterior and given no sense of the thing outside being intimately connected to the inside, which seems to the thrust of the "or maybe" part of the question. "Extrinsic" is good except for the connotation it has of "inessential," which the word gets from its antonym "intrinsic."
If you're content with a technical term specifically tied to the spiritual, then there's always "ectoplasmic."
The idea was uncanny
Though the title of the OP merely asks for a single word that would describe something “outside of oneself,” the body of the OP is somewhat more elaborate and describes this something as of "divine inspiration, dumb luck, etc." For this reason, and despite Parthian Shot's apt and officially selected answer ("external"), I would also suggest the adjective "uncanny" as a suitable descriptor for the experience of something unusual, or even preternatural, whose origins lie outside of the normal, day-to-day, self.
uncanny adjective: strange or mysterious, especially in an unsettling way. "an uncanny feeling that she was being watched"
synonyms: eerie, unnatural, unearthly, preternatural, supernatural, otherworldly
(Google)
Extracorporeal has the exact meaning of something being outside one's body.
Merriam-Webster (http://www.merriam-webster.com/dictionary/extracorporeal):
extracorporeal
adjective ex·tra·cor·po·re·al \-kȯr-ˈpȯr-ē-əl\
Definition of EXTRACORPOREAL
: occurring or based outside the living body "the heart-lung machine maintains >extracorporeal circulation during heart surgery"