know one's own mind

know (one's) own mind

To be firmly resolute and confident in one's ideas, intentions, plans, or opinions. I've never worried too much about the effects of peer pressure on Kelly, as she really knows her own mind on what's right or wrong.
See also: know, mind, own
Farlex Dictionary of Idioms.

know one's own mind

Be certain about what one wants; be decisive. For example, Don't ask him; he's so tired that he doesn't know his own mind, or She certainly knows her own mind when it comes to giving stage directions. This term was first recorded in 1824.
See also: know, mind, own
The American Heritage® Dictionary of Idioms by Christine Ammer.

know one's own mind, to

To be certain of one’s opinions or plans; to be self-assured. This term has been known since about 1700. Jonathan Swift included it in Polite Conversation (1738), “You don’t know your own mind,” an accusation still often voiced in just this way.
See also: know, own
The Dictionary of Clichés by Christine Ammer
See also:
  • know (one's) own mind
  • know your own mind
  • stand by (one's) guns
  • stick by (one's) guns
  • stick to (one's) guns
  • stick to guns
  • stick to one's guns
  • stick to your guns
  • mean well
  • peek out