This couple broke up (separated), but he could never get over it (forget about her). They’re not together, but he still has her photo beside him and her lipstick mark on her last coffee cup (he didn't want to clean it because he wanted to have a memory of her), because he never wanted to forget her. She, on the other hand, seems to have got over it and has a new life ("you excelled at being free").
Pride kept him away, but after a long time, now he is ready to give up and swallow his pride ("now it's time for me to give up") and deeply regrets everything that happened. All he wants now is to be together again. He’s not very sure if it was his mistake or hers, but all the same he wants to make up for anything wrong he made. He is willing to do anything to have her back, and this time, forever (for good)