Interview With The Vampire..I was reading it at a nice time in my life, and it was a wonderful book! Even alone, I highly reccommend it.
Towards the end, the main character (the interviewee), in his story, finalized living with his second long-term "partner" (another male vampire, who was geunuienly affectionate towards him). The main character slowly, as they traveled the world and saw everything that there could be to see, lost the spark to him that his "parter" had saw. He lost interest, and reason, and care for most everything. His "partner" commented on this, asking basically if he still is who he once was. The main character said no. Upon that, his "partner" stood, left, and was never seen again. He presumably ended his immortal life.
To lose someone so shining, and to be able to let someone go in that moment only to regret it for an eternity... These ides and more made me cry so hard! I really had to re-think my position on the concept of immortality.