In lieu of describing this Sundance standout starring Alfred Molina and John Lithgow, I offer this amazing quote from a review by critic James Rocchi of The Playlist:
It has been noted that early couples say “I love you” with the force of a thousand exploding suns, but that long-standing couples say “I love you” in a way that can also ask, unspoken, if it was you who happened to leave the goddamn garage door open again. That kind of love is rarely seen on film, and hard to portray when it is; Molina and Lithgow make that happen here, with all of the feeling and fights and closeness that a real couple would have.
The Screen Life 