keep to oneself

/K IY1 P T UW0 W AH0 N S EH0 L F/
verb
  1. 1

    To purposely avoid interaction with others; to be introverted.

  2. 2

    To refrain from telling or giving; to keep secret, or refuse to share.

Source: https://en.wiktionary.org/wiki/keep%20to%20oneself