But screw your courage to the sticking-place
Be steadfast and of good courage.
From Shakespeare's Macbeth, 1605:
But screw your courage to the sticking-place,
And we'll not fail.
It is thought that Shakespeare was making the allusion to the screwing-up of the peg of a musical instrument until it becomes tightly fixed. If that is so then the phrase's meaning is 'keep screwing up your courage until it reaches the sticking place' not, as is usually thought 'affix your courage to the sticking place'.
See other phrases and sayings from Shakespeare.