Know One's Own Mind Meaning

(idiomatic) To clearly understand one's own feelings, intentions, preferences, etc; to know precisely what one wants; to be decisive or determined.

Example: 1886, Louisa May Alcott, Jo's Boys, ch. 1:
  Demi knew his own mind, however, and tranquilly carried out his plans, unmoved by the tongues of the anxious mammas or the jokes of his mates.
1889, Wilkie Collins, The Legacy of Cain, ch. 54:
  He sadly wants strength of purpose; and, like weak men in general, he only knows his own mind when a resolute friend takes him in hand and guides him.
1892, W. H. Hudson, Fan: The Story of a Young Girl's Life, ch. 18:
  "Wise girl—strong-minded girl, knows her own mind," muttered Mr. Churton.
1920, P. G. Wodehouse, The Coming of Bill, ch. 3:
  He was the strong man who knew his own mind and could not be shaken.
1973 Aug. 13, "The Law: The Little American," Time:
  "I'm a conservative Republican who hasn't approved of any conservative Republican in years because most conservative Republicans aren't conservative enough for me." So says John J. Wilson, 72, who knows his own mind and does not hesitate to speak it.
2004 June 11, Margaret Thatcher, "Remarks by Former British Prime Minister Margaret Thatcher," New York Times (retrieved 26 Dec 2011):
  Ronald Reagan knew his own mind. He had firm principles - and, I believe, right ones. He expounded them clearly, he acted upon them decisively.