The best, most heartbreaking moment of the movie...

is when Billy is in his parent's house, and his dad has gone to 'sing' Layla a song. When everybody has left the table, Billy is on his own; he swipes his childhood photo off of the table and takes a glance of it. It then cuts back to the father. When we come back to Billy, we see he's still looking at the photo and seeing himself as a child with his pet, no worries and no stress. All he see's is a little kid, carefree and innocent, and for the first time in the movie up to that point, we can see him sobbing.

It's pretty clear to me that seeing this photograph of himself after spending years in jail breaks him down and reduces him to tears because he is unable to contain all of the disappointment and heartbreak his adulthood brought him.

Very small moment in the movie, but most certainly one of the best. Love this movie.