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.
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.
know your own mind
be decisive and certain.know your own ˈmind
know what you want or like: At 25 you’re old enough to know your own mind and make these decisions for yourself.