Invictus
The conqueror's mindset...
The popular poem by William Ernest Henley comes to mind with this singular word.
It comes from two (2) root words, which combined mean “not to [win/conquer]”.
“Not to conquer” the mind or spirit.
You need to agree with it and believe it — you need to have a mind that will not be put down.
I agree for the most part with William’s poem, except, as a christian, this is what I do know:
I thank whatever gods may be
For my unconquerable soul.
I thank my creator JEHOVAH, for He keeps my soul.
I am the master of my fate,
I am the captain of my soul.
HE is the master of my soul.
For ye were as sheep going astray; but are now returned unto the Shepherd and Bishop of your souls.'
1 Peter 2:25
https://www.bible.com/bible/1/1PE.2.25.KJV

