Mine would have to be "How to Save a Life" by The Fray. I left my entire family due to abuse from both parents, but my brother and I still maintained contact and hung out and whatnot, but one day he just blew me off for a hangout, and never spoke to me again. I called and texted to no avail. One night, I drove the hour down to his house where he still lived with my parents. It was late at night so my parents were asleep, but his window was open and the light was on. He was watching a movie on his computer. I threw pebbles at the window and called out to him for ages, but he wouldn't come to the window. That was the last time I tried. It's been almost 9 years now. That song gets me every time. "Where did I go wrong? I lost a friend somewhere along in the bitterness. I would have stayed up with you all night had I known how to save a life."