The essence of Gilgamesh transcends time.  Each and every one of us, at one time or another, will face uncertainty.  We struggle with questions that we cannot answer; "is there a God?" where do we go when we die?" "The Epic of Gilgamesh" tells  the story of the human experience.  His journey is our journey, in that through his life experiences he gains wisdom, hopefully we do as well.   His questions of immorality and why his friend dies are not directly answered, however by the end of the story they do not have to be.  The Epic of Gilgamesh is not about answers...it is about human beings and their desire to understand the purpose of their existence.  Gilgamesh's true heroism does not stem from who he was, or what he did...  what makes him truely heroic is the moment he "understands" his humanity, his place in the world. 

The overall impression conveyed by the conclusion of "Gilgamesh" is that the protagonist has reached a more mature understanding of his place and purpose. He had wanted to be immortal. The "tears" are both of regret and joy. He regrets the foolishness of the past and also the realization that immortality does not mean physically living forever. The joy in his tears is probably partly because he has made a mark in the world of lasting effect. He has come to terms with his mortality and what he has been able to accomplish.