I like to listen to a lot of downtempo things to help me stay calm. Things like Tycho, Tim Koch, Proem, Tipper, as well as classical music.
The Cure usually uplifts my spirits but if I'm feeling like my mood is teetering,
If I'm already in a bad mood, I really love intently listening to (on loud decent speakers!) a track called Kétsarkú Mozgalom, which roughly translated from Hungarian means "Bi-polar", or "2 poles" movement.
It's here if anyone wants to check it out but be warned, it's a very intense piece, as well as challenging, if you've not listened to anything like this before, but I honestly think it's a masterpiece! https://www.youtube.com/watch?v=zX7rjy-qFcI. It changes quite a lot so if you can sit through it, kudos to you

My boyfriend finds it surprising that a track like this would be helpful instead of acting as a trigger, but as it goes faster than racing thoughts do during an episode, it allows me to feel the anger and kind of release so for me it's therapeutic. It has strong contrasts between speedy highs and chaos (although a somewhat ordered), with more and crushing lows and moments of calm (the strings). Lyrics: "I remember being happy here. I remember being sad here".
My boyfriend isn't BPD but has depression issues - if I hear him play stoner rock, I know he's on a downer, otherwise he mainly listens to progressive house!