Imagine someone at school makes a mean face at you when you answer correctly in class. Are you going to stop answering because of that? Retreating means letting other people's mean faces decide who you are. But Proverbs says: the lion doesn't do that! It knows who it is, and it simply walks.
Jesus never retreated in the face of anyone's opinion. He spoke the truth in love, moved forward with purpose, and knew exactly who He was. We are children of God, and children of God don't need to retreat!