In this song, the Avett Brothers tackle depression in a way that only those that have journeyed through the illness understand. On one hand, it's a beautiful depiction of the struggle to find happiness even when you can't understand why happiness seems elusive. On the other hand, it's just a finely written song.
When the Avett Brothers released their latest album, they also released some accompanying commentary. Here's the explanation of "Winter in my Heart."