“This I choose to do,” she croaked, her breath leaving little clouds in the air. She cleared her throat and started again. “This I choose to do. If there is a price, this I choose to pay. If it is my death, then I choose to die. Where this takes me, there I choose to go. I choose. This I choose to do.”
It wasn’t a spell, except in her own head, but if you couldn’t make spells work in your own head, you couldn’t make them work at all.

Terry Pratchett (1948–2015) English author

Discworld No. 35, Wintersmith, ch. 1 [Tiffany] (2006)
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