slightly formal to not tell other people about your opinions or plans.
He was a quiet man who kept his own counsel.
keep (one's) own counsel
To not share one's thoughts or plans with others. I'm just naturally a private person, so I keep my own counsel.
keep one's own counsel
Fig. to keep one's thoughts and plans to oneself; to withhold from other people one's thoughts and plans. Jane is very quiet. She tends to keep her own counsel.I advise you to keep your own counsel.