He has nothing left to live for it is almost like he died as well. Another key theme was love as a force.
Enkidu was a human living like an animal. The only way to relieve him of his animal instincts was for him to make love to Shamhat. The outcome of this meeting caused the animal kingdom to reject Enkidu and for him to become and live likes an actual human being. Someone was forced to make love with someone just to become "human."
Gilgamesh was the ruler of Uruk and best friends with Enduki. Yet, when Enduki died, Gilgamesh fell apart. The most interesting thing was that Enduki's death was foreshadowed by a dream Gilgamesh previously had. He dreams about a meteor, which his mother explains to him is the companion and friend he will have soon. The dream Gilgamesh had foreshadowed the death of Enkidu ever so slightly, it didn't make his death perfectly clear but it left some room for thought.
When Gilgamesh went on his journey he was sent out to find Untapishtim. Untapishtim means "he who saw life." This place defines the story of Gilgamesh perfectly. He has been through a lot in his life and it was only fitting for him to go find Untapishtim. He witnessed his best friend die and his life crumble right beneath his
feet.
Gilgamesh was a very multipart epic with many lessons to be learned. It had a number of subliminal messages, which takes complete twists throughout the epic. The themes were also very good lessons to life and future epics.