One problem when you’re sad is that listening to a song that will usually boost your mood will seem sickeningly sweet. However, listening to happy music is often a really powerful way to get you out of a funk. Listening to sad music can sometimes feel cathartic, but sometimes it can just reinforce the negative emotions. It can make you feel sadder or angrier, confirming your view that the world sucks, people are terrible, and nihilism is probably correct.
A way out of this problem is to keep a list of songs that start sad or angry, then slowly morph into happy or inspirational tracks. Whenever you run across a song that fits this criteria, add it to your list, then, when you’re in a terrible state, you can pull it up and listen to it. The melancholic start will fit with your current mood, but like a nicer version of slowly boiling a frog, you’ll gradually be shifted into something more uplifting.
I'm an effective altruist who co-founded Charity Science Health and Charity Entrepreneurship.