Clemont's problem isn't that he is not brave enough, it's his low confidence and self-esteem. Surely Clemont is brave, but it is his low self-esteem that makes him feel like he has to live up to something or someone. This episode proves that. He thought Chespin hated him and was willing to leave Chespin with some random old lady if it meant that Chespin would be happy. He clearly doesn't think high of himself if he acts like that. He literally though Chespin would be better off with her than with him.