What is the main conflict in The Art of Racing in the Rain: A Novel by Garth Stein?

The novel begins at the end of Enzo's life. He is looking back at some of the most critical moments of his existence as a dog and philosophizing about what he has learned on his journey so far. Enzo is old and ill but his spirits are buoyed by the lovely memories he has collected along the way. And even though he is accepting that his time is near, Enzo is nonetheless disappointed that he cannot take his memories into the next life with him. Enzo is convinced that he will be reincarnated as a man, with thumbs. Being a man is Enzo's ultimate dream and there is nothing more important to Enzo than leaving this life and beginning the next life as smoothly and as soon as possible.