Compare and contrast the closing sequences of "Rembrandt" and "Raging Bull." How is it they represent the biopic subject of self determined loner?

Both Rembrandt and Raging Bull end with the protagonists looking into a mirror talking to themselves. Rembrandt is painting yet another self-portrait, and he  the line, "Vanity is vanity."
Jake LaMotta is trying to psych himself up before doing a comedy routine on stage. He says to himself, "You coulda been a contender," and then boxes the air while repeating, "I'm the boss, I'm the boss."
Rembrandt's second wife-to-be had died years earlier, and he dedicated his life to his art until the day he died.
LaMotta was always a jealous, angry man, and he drove away all of his family and friends by being violent.
Both men chose to be alone through their actions, and looking into a mirror talking to themselves is a great way to show that they have no one left in the world but themselves.