I mean he’s being completely and literally torn apart here because very real pieces of him are going out the door with her, and the bitterness on his tongue is a foretaste of his own world colapsing in around him, suffocating him as he struggles to come to terms with what is happening. But he gets himself together enough to say, but you said you’d love me forever. At least this causes her to stop in the door, and she turns round, and he’s waiting for her to Come Back In and Realize She Made A Mistake, and to Make It All Alright Again. Or just… explain. But in fact all that happens is that she slips a puzzled look on her face and she says, it sure felt like forever. And off she goes. Leaving him alone on the stairwell. Alone, his heart shattered.