Bipolar 2 here, hypomania and depression + mixed episodes. This is purely based on own experiences btw, I’m no expert, nobody probably is.
Mindfulness can definetly help, but it depends on what mood your already in. I’m sure you know this (not trying to sound like I’m better or anything) but bipolar is not really something you can control with your mind, as it is a disorder of the mind, if that makes sense. Like if I’m hypomanic I won’t use mindfulness simply because I can’t really concentrate on doing just one thing. Mindfulness demands a certain level of concentration and patience, which a hypomanic/manic person won’t necessarily have. I can be concentrated and obsessed with something, but it’s rarely productive or helpful. Even breathing techniques don’t appeal while hypomanic, it’s just too messy. You feel unbreakable and invincible all the time, nobody can stop you. I even get these episodes when I «believe that fate has a plan for me» so I can’t die (lol I know) no matter what, so I try everything, even things I know are dangerous. I think mindfulness might stimulate this kind of behaviour while manic/hypomanic, cause it boosts you up and the more you boost, the more manic you become and eventually the harder the fall gets.
While depressed I don’t have energy to do basic stuff like eat and I have a total different mindset where «nothing is worth it», so mindfulness is the least I think about. Depression is very physical for me as well as I get migraines and fever like symptoms, and when you feel like that the idea of «bettering yourself» is very distant. However, I’ve gotten better at meditation and mindfulness techniques lately. This past year I’ve actually used mindfulness videos/audio on youtube while depressed to feel less alone. Cause I really want to be alone while depressed, but I don’t want to feel alone. Meditation helps with that.
Btw I’m not on medication, I used to do therapy with several doctors and psychologists, but now I only use group therapy. I might turn to medication though, as the older I get (I’m 24) the worse it becomes. I’d love to use mindfulness and meditation all my life, as I hate medication of any kind, but I’m not sure how much more healing of my own that I can do.