be (one's) own man/woman/person

To act, think, or work independently; to not accept or be swayed by outside influences. You can't just accept everything you read in the media—you have to be your own man. When I was younger, I would do anything my friends were doing, but I'm my own person now. You won't be able to manipulate her—she's really her own woman.

own man/person, to be one's

To be in charge of one’s own affairs and actions. This term is very old indeed and may be obsolescent. Chaucer, who often portrayed strong women, used it (Troilus and Criseyde, ca. 1374): “I am myn own woman wel at ese.” A modern equivalent is to do one’s own thing.