"All By Myself" the original and the version by Celine Dion. I remember playing it over and over and over...all evening while I was all dressed up and eating the meal that I had prepared for someone else. (I got annoyed with him at the last minute and told him not to come over. I had borrowed table cloth and napkins from work and wine glasses and flutes from my mother...made him lasagna and cupcakes and had dinner and dessert wines and a sexy dress in many shades of his favorite color. It was his birthday.) I listened to the original version. Oh, the drama of the early 20s.
ETA: Oh, yeah--"I Was Meant for You" by Jewel is another one that accompanied me in that relationship.
O. M. G. How could I forget "Torn" by Natalie Imbruglia? Oh, I cried. Same relationship.