He lost his love, but not his will to live. 

Kangin writes one final letter to his lover before deciding it was time to live his life, if not for himself, then for Jungsu, for both of them. He writes all the things he never said and could have said all in this one letter, this one last letter. 

Jungsu, You know i can never move on from you but i think that maybe, it's time for me to go on living because life is still passing me by. If I can't live for myself then I can at least pick up where you left off.