off one's guard vs off your guard

off one's guard and off your guard both are adjectives.

Word	Noun	Adjective	Verb	Adverb
off one's guard	No	Yes	No	No
off your guard	No	Yes	No	No

As adjectives, off one's guard and off your guard are synonyms defined as:

Other synonyms of off one's guard include napping, off-guard, off guard, off her guard, off his guard.

off one's guard (adjective)	off your guard (adjective)
not prepared or vigilant	not prepared or vigilant