Know your own mind
Definition 1 of 1
Pro Tip 1/3Personal Conviction
Expresses strong personal certainty, not influenced by others. 
Despite the debate, she knows her own mind and won't be swayed.
Pro Tip 2/3Decision Making
Highlights one's ability to make decisions independently. 
He knows his own mind and has already chosen his major.
Pro Tip 3/3Assertiveness
Shows confidence and assertiveness in stating preferences or opinions. 
She's not easily influenced; she really knows her own mind.