I would welcome some input about how meditation helps.
There's a lot to say about this and I'm not an expert. However, I do remember those first really bad months. I was really falling apart and just trying everything I could, and meditating helped me.
One really common method for settling into meditation is to "scan" your body, notice all the sensations in it. Another is to notice the sounds around you. What these things have in common is that they are happening in the present. Meditation anchors you in the present. From a certain perspective there is no separate past or future. The past has expired and ceased to be; the future isn't here yet. When we're "living in the past" or ruminating, we're doing it from the present. Thoughts of what happened, what's happening somewhere else--they are just that: thoughts, like clouds in a blue sky that you can observe and wonder about. Think of them from the outside and they lose some of their power over you. When you are in a state of crisis over your pwBPDex, you are living inside those thoughts and your perspective is being warped.
Or if that doesn't do it for you, think of this: I know my mind was spinning like a top a lot of the time. It needs a rest. Meditating is, if nothing else, a breather for your busy mind.
Right now your body is coursing with cortisol--a stress hormone. High amounts of it for a long time are really bad for you: bad for your digestion, your heart, your sleep. Meditating lowers the amount of cortisol you produce.
I don't know. When I was in the thick of it I was just trying everything, because I felt like I had nothing to lose.