From the Paul Thomas Anderson movie Magnolia, for which Aimee Mann did most of the soundtrack, this song comes at a sad, emotional crossroad in the movie. In fact, let's open this post with that very sad, emotional crossroad. The moment could have been absurd, but it wasn't.
But this song is so so much more than a soundtrack song - especially since it wasn't written for the soundtrack and had PREVIOUSLY appeared on the Jerry MaGuire soundtrack. It is in and of itself an emotional powerhouse with a real downer of an ending. P.T. Anderson has said that Aimee Mann's music inspired Magnolia, so it is likely that this song was part of that inspiration.
Listen to Aimee sing it herself, without the cast accompaniment.
She still performs the song, which is a fan favorite. Because of course it is.