pluck up the courage to (do something)
To bolster one's courage or emotionally prepare oneself enough to do a frightening or overwhelming task. I want to ask Sarah out on a date, but I'm trying to pluck up the courage to do it! I know he's terrified of speaking in public, so he's having a drink to help pluck up the courage to go on stage.
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.