know one's own mind

know one's own mind idiom
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.

The American Heritage® Dictionary of Idioms by Christine Ammer. Copyright © 2003, 1997 by The Christine Ammer 1992 Trust. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.

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