pluck/screw/summon up courage
pluck up someone's courage
to bolster someone's, including one's own, courage. I hope you are able to pluck up your courage so that you can do what has to be done. Some good advice from a friend helped pluck up my courage.
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.