"possess himself" is a grammatically correct and usable phrase in written English.
It can be used in various contexts, but it typically means to take control or ownership of oneself or one's thoughts/emotions. Example: After a long period of self-reflection, he was finally able to possess himself and let go of his past mistakes.
In an address at the Commonwealth Club, in September, 1932, F.D.R. urged "statesman and businessman" alike to recognize that "our government … owes to everyone an avenue to possess himself of a portion of that plenty sufficient for his needs, through his own work".
Our government formal and informal, political and economic, owes to every one an avenue to possess himself of a portion of that plenty sufficient for his needs, through his own work".
That means it is ethical for a prosecutor, according to the ABA, to ask a jury to pronounce a defendant guilty with a degree of certainty that the prosecutor may not possess himself.
Having possessed himself of papers to show that he was a freeman, he went to Washington, and while there, as he avers, was fraudulently conveyed to a slave-pen.
Sime wrote of Reed's particular empathy with the young: "He possessed in himself the healthy freshness of heart of boyhood ... and could place himself sympathetically at the boy's standpoint in life".
When he mounts his rocking horse he becomes a child possessed, imagining himself in a real horse race and infallibly predicting the winner.
According to Wells's own brief, slightly ashamed account in the Postscript, he "never found any great charm in Rosamund", but "she talked of love and how her father's attentions to her were becoming unfatherly", so he decided to protect her from incest by possessing her himself.
Attendances at the church were small until, during one of the services, Prince acted as if he was possessed, throwing himself around the church.
Julius, although unsatisfied with his gains, did not himself possess sufficient forces to fight the Republic; for the next two years he instead occupied himself with the reconquest of Bologna and Perugia, which, located between Papal and Venetian territory, had in the meantime assumed a status of quasi-independence.
As the artist, however, Marsh is able to outdo his rivals and, triumphantly, possess her for himself — in imagination and on canvas if not in reality.
In 1466 he detected a plot to overthrow his rule, and, showing more courage than he was supposed to possess, he had himself borne on a litter to Florence, where he defeated his enemies.
