It is the purpose that makes strong the vow; But vows to every purpose must not hold.

I am sure care's an enemy to life.

This day's black fate on more days doth depend; This but begins the woe, others must end.

For she had eyes and chose me.

Nothing routs us but the villainy of our fears.

Believe then, if you please, that I can do strange things. [Act 5, Scene 2]

Or art thou but / A dagger of the mind, a false creation, / Proceeding from the heat-oppressed brain?