muster up

develop；gather鼓起；奋起

He mustered up courage to climb the cliff．他鼓起勇气攀登那个峭壁。

Muster up yodr courage．The difficulty will soon be overcome．鼓起勇气来，困难很快就会克服的。

He mustered up all his courage for the ordeal．他鼓足勇气去经受严峻的考验。