Being a man means taking control of your life and being responsible for yourself. A man does as he chooses, while a boy does as he should. However, some men never make this leap; they struggle with carving out their own path in life.
So they flounder. Because they've never actually figured out what they really want in life, they end up picking life goals they think they should have simply because everyone around them–/society/television/family/religion–tells them they should have those goals. In short, they should on themselves.