This is probably the highest due to the frequency I listened to it while writingCure For Pain. One of the overarching themes in Cure for Pain is Ty's longing to be seen by Mary, for who he really is, and Iris sums it up beautifully. In the book Ty just wants the time he has with Mary. The two have a connection that most don't understand. Ty senses the sincerity and goodness in Mary, and he's drawn to that. She is the cure to the pain he is in; the pain of self loathing. He is living a life with a past he's ashamed of and a present he has to hide from everyone, while being someone who he desperately doesn't want to be. When he's with Mary, he can live in a moment where none of that matters.
Yet, he knows it wont last forever, the odds are against the budding relationship from the start. It's not just people who have warned them both off, it's Ty's own secrets and his past that endangers any possible future he could have with her. Even though things may not be as they seem, the danger he has put himself in is very real, and he knows it puts Mary at risk too.
I listen to Iris and feel Ty's emotions. It was one of my greatest inspirations when creating his character. It's such a beautiful song that expresses the desire to have a true connection with one person and for that person to see past your flaws and love you for the person you are.