summon up (one's) courage
To emotionally prepare oneself to do a frightening or overwhelming task; to bolster one's courage. I'm really nervous about asking Sarah out on a date, but I just need to summon up my courage and go through with it. I know he's terrified of speaking in public, so he's summoning up his courage with a stiff drink.
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.