self-possession vs possession

self-possession and possession both are nouns.

Word	Noun	Adjective	Verb	Adverb
self-possession	Yes	No	No	No
possession	Yes	No	No	No

As nouns, self-possession and possession are synonyms defined as:

self-possession and possession: the trait of resolutely controlling your own behavior

Other synonyms of self-possession include self-command, self-control, self-will, will power, willpower.

self-possession (noun)	possession (noun)
the trait of resolutely controlling your own behavior	anything owned or possessed
	the act of having and controlling property
	(sport) the act of controlling the ball (or puck)
	the trait of resolutely controlling your own behavior
	a territory that is controlled by a ruling state
	a mania restricted to one thing or idea
	being controlled by passion or the supernatural