I've found that the more I listen to happy music, the more I am affected to it. The more I listen to sad music, the more sad I am. Despite the fact that I might listen to happy music when I'm happy, and sad music when I'm sad: that's the reason why I'm listening to the music in the first place. The mood of the music listen to truly affects your mood, because if you think about it, you probably have never listened to sad music when you're happy, because you didn't want to be sad: because you knew that you would've been affected by the music.