What happens when Emily revisits her past life in Our Town?

Like all the spirits in the play, Emily can go back and relive moments from her past. But what makes this such an emotionally painful process is the fact that she cannot experience the past by itself; she experiences the present and the future at the same time.
This means that when Emily revisits her 12th birthday, she cannot revel in the moment; the whole experience is just too overwhelming for her. Emily realizes to her great sadness that she cannot hold on to the world forever, because as the Stage Manager explains, the dead don't stay interested in the living for very long. Gradually, they get weaned off the earth and all the attachments they had to it when they were alive. As the spirit of Emily ruefully reflects, the living—and she would include her former self in this—don't really appreciate how wonderful life is and how important it is to seize each and every fleeting moment.