keep oneself to oneself, to

to remain aloof. He does tend to keep himself to himself. Keep yourself to yourself, and you'll be all right there.

see under keep to oneself.

To be reserved and aloof, avoiding the company of others. Samuel Richardson used this phrase in Clarissa (1748), and it was repeated by numerous writers, some of whom pointed out that it was a quintessentially English form of behavior. “He kept, in popular parlance, himself to himself. Like many policemen, Dunday thought,” wrote British novelist Robert Barnard (Death and the Chaste Apprentice, 1989).