“day 21 – a song that you listen to when you’re happy.”
Compared to anger, happiness is a relatively simple emotion: it doesn’t need analysis or observation, it simply is. What else can you say when you are happy, other than affirm it and live it? This is a song I listen to when I am happy.
(POSSIBLE SPOILERS: If you intend to watch The Wire, which you should, I’d recommend you not watch the below. This is the closing montage for season 2.)