screw (one's) courage to the sticking place
To remain bold, resolute, determined, and courageous, especially in the face of possible danger, difficulty, hardship, or adversity. Taken from a line in Shakespeare's Macbeth: "We fail! But screw your courage to the sticking-place, and we'll not fail." Men, some of us may not make it back alive, but such is the nature of war; so screw your courage to the sticking place and show them what you're made of! I'm really nervous about asking Sarah out on a date, but I'm going to screw my courage to the sticking place and ask her by the end of the day.