"Paris, Texas" ends with the main character reuniting his son with the boy's mother, but then driving away without even a good bye. It's a self imposed loneliness that I can really relate to.
"Miller's Crossing" the film ends with the inevitable end of a friendship. As much as the main character cares about his friend, he cannot support his foolishness.
"Crimes and Misdemeanors" the fact that some people can live happily with their own crimes is pretty dark. I love the ending quote that our lives are the sum of the small choices we make every day.
"Songs From the Second Floor" a man with rather questionable ethics bemoans the fact that he is haunted by the ghosts of his past.
"Another Year" a woman recognizes the futility of her hopes, but even still, you know she won't change.
"In A Lonely Place" a perfect summation of how a good relationship can be destroyed by suspicions. The ending is particularly devastating to me.
"The Blue Angel" a man who should know better allows himself to be manipulated to flatter his vanity.
"Brief Encounter" two people who really love one another, but are married to other people cannot act on their emotions.
"In the Mood For Love" basically "Brief Encounter" in Chinese.
"Fargo" some people are just banally awful.
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Never let the weeds get higher than the garden,
Always keep a sapphire in your mind.
(Tom Waits "Get Behind the Mule")