I love the movie “Forgetting Sarah Marshall.” It’s funny, irreverent, but totally true. And, again, it’s funny.
One, like many real life relationships, there are no “bad guys” aka real antagonists among the main characters forming the no-longer-together couple of Sarah and Peter. The movie viewer isn’t invited to hate them. Even the rock musician character of Aldous as the new love interest of Sarah is not meant to be hated.
Two, although there’s a big breakup scene early in the movie, it’s revealed through the plot that it was a relationship slowly dissolving and, really, neither Peter nor Sarah were all that happy in the relationship. That’s like real life too.
Here’s an example from the movie itself. It’s one of many.
http://www.youtube.com/watch?v=k7axkJnK1Xk