To me the movie was about living in the moment versus creating something that lasts. Colm wants to play music that lasts after he dies. His time spent with Padric directly conflicts with that goal.

When Padric and Colm spend time together, he loses a finger. This makes playing music much more difficult. It’s a very dark ironic bit, when he goes back to spending time in the moment, it negatively effects his ability to creat lasting music. In this case, it a very physical manifestation of the theme of the film.