You could write a song about some kind of emotional problem you are having but it would not be a good song in my eyes until it went through a period of sensitivity to a moment of clarity. Without that moment of clarity to contribute to the song it's just complaining.
There's a darkness under 'The Hangover' because ultimately there's a missing person and it's not really that funny. There's a sort of darkness under it that I love and still people are laughing as hard if not harder than they did in 'Old School.'
