Jimmy screwed up his courage and gave Lisa a heart-shaped box of chocolates on Valentine's Day.
screw up (one's) courage
To emotionally prepare oneself to do a frightening or overwhelming task. I'm really nervous about asking Sarah out on a date, but I just need to screw up my courage and go through with it.
screw up one's courage
Fig. to build up one's courage. I guess I have to screw up my courage and go to the dentist. I spent all morning screwing up my courage to take my driver's test.
pluck/screw/summon up (your/the) ˈcourage (to do something)
force yourself to be brave enough to do something: I had liked her for a long time, and eventually I plucked up the courage to ask her out.I finally screwed up my courage and went to the dentist.