"He deems himself" is correct and usable in written English.
You can use this phrase when you want to express someone’s opinion of themselves. For example, "He deems himself successful despite the many challenges he has faced."
Though he deems himself "not complicated enough" to debate why the US carmaker is on the brink of extinction yet again, Greenfield avowed with a grin that "automobile people are tough people" - and that the 100-year-old General Motors name would live on.
Perhaps some time later, when he deems himself "ready," he'll reappear.
This feeling of uselessness eventually leads to thoughts of suicide, though he deems himself too much of a coward to go through with it.
But because he was "born a Jew," studied the Holocaust and has spoken in front of the Anti-Defamation League, he deems himself qualified to weigh in on the matter.
He deemed himself ready to go before the team left for California.
Although every client wanted to be exclusive to Bob, he insisted on sharing every single relationship he ever had and only considered himself a success when he deemed himself "irrelevant" … which of course he never was.
In any event, he deemed himself the injured party and skipped the parade, heading instead to the Bronx for linguine marinara.
As Trump spoke, he deemed himself the "law and order" president ― and promised that "crime and violence" would "come to an end" once he becomes president ― all the while probably hoping Americans won't look at the facts.
He happily deemed himself "laissez-faire" in 1976.How did these ideas become mainstream?
He frequently appears on magazine covers, blogs with all comers at a popular Web site and deems himself a historic figure in the state-dominated media business.
Mr. Stein, at age 72, deems himself an "old man".
