There is a reason it is called a "tragedy" instead of a story. Yet, as for other reasons, one of the main ones is their fatal flaw. The great heroes of old Greek literature were meant to be built up, do great things, and then fall horribly, encouraging the ancients because it made them feel better, knowing that heroes did so poorly as well. The hero always had an extreme fatal flaw (anger [Hercules], lack of focus [Theseus], loyalty [Jason]) that would lead to them making a choice that would secure their death and destruction, if not worse. Hope this helped.
