keeps to oneself

To keep to oneself means to remain private and avoid social interaction, often preferring solitude: After the breakup, he kept to himself for a few months.

Related

reflective · independent · autonomous · shy · secretive · cautious · discreet · self-contained · enigmatic · contemplative · aloof · antisocial · nonconformist · solitary · hermetic · insecure · quiet · reclusive

Opposites
social engagement

keeps to oneselfoutgoing

Sociable and unreserved

gregarious · sociable · extroverted · social butterfly · life of the party

information sharing

keeps to oneselfovershares

Divulges too much

open book · tells all · gossips · forthcoming · candid

Familiarity
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