The philosopher Slavoj Žižek on why ‘Melancholia' by Lars von Trier is actually an optimistic movie.

'Lars von Trier's Melancholia, I think, it's a basically, I'm not kidding, optimistic film, even as we know at the end the planet Melancholia hits the earth, we all die.  But I find something beautifully poetical in the attitude of the main person, Justine, played by Kirsten Dunst, no, this inner peace, how she accepts this.  

I claim that we should not read this as kind of a pessimism. "Oh, we all die.  Who cares?"  No, if you really want to do something good for society, if you want to avoid all totalitarian threats and so on, you basically should go . . . we should all go to this, let me call it--although I'm a total materialist--fundamentally spiritual experience of accepting that at some day everything will finish, that at any point the end may be near.  I think that, quite on the contrary of what may appear, this can be a deep experience which pushes you to strengthen ethical activity.

The result of this experience is not, "Oh, the end may be near, so let's kill, let's just enjoy," and so on.  No, it's the opposite. Again, paradoxically, I claim it's not a superficially but profoundly optimistic film.'