Really great question(s)!!!! I have had BPD, massive depression, heck everything all of my 65 years on this rock. To be 100% honest, I am still in the process of "mood stabilization" yet. NOT being a downer at all but it is tough, at least for me.
I have tried prescript drugs, yoga, a lot of things and what seems to work best for me is being "mindful" of myself. My definition of this is: 1) when I know my mood is starting to swing all over the place, I stop everything and take a deep breath and see what is going on and why am I reacting the way I am 2) Sometimes it is just better if I excuse myself and take some time to regroup my thoughts.
Maybe that is one of the reasons I do not have any friends, as I am perceived to be different in my ways.
We are ALL together in this, we are ALL ONE, we are ALL the same, as we are ALL sentient beings I love and care for all and especially here on SS.
Take care my good friend @sickofbeinghere, as I send you lots of hugs, well wishes and a bright blue sunny sky!!
Walter