I have one friend. So clearly, i am doing much better than both of you.......
The ups and downs, generally come from idealisation and black and white thinking. Drugs, can't really cure this for most of us....they just mask it or numb it. I don't know what type of BPD you have or are......but if you have rapidly shifting moods, chances are it's from your environment including your thoughts.
If i really want a piece of pizza, and then i go to the fridge and there is no pizza left. I forgot i ate it last night.......and then, on the way back to my room, i catch a glimpse of myself in the mirror and don't like what i see..........there is a very good chance, that 2 minutes later, i'll be thinking of killing myself. Even if i don't "think" i care about the pizza, or the mirror............that'll be all it takes to get those negative juices flowing..........
A friend calls.....suddenly i'm back on top of the world..........that same friend, doesn't say "goodbye" with the proper enthusiasm.......i'm down again.
For me, i am up and down........basically with the wind. My mind, tries to attach ideas to why i feel the way i do...........but it's kind of like coming up with a story, to make sense of the story that actually makes no sense.
Kind of like the whole "i love him, i hate him" thing. Depends on if he is smiling at you or not, right?
That is black and white thinking...........and that is essentially what this is all about.
We have to learn to separate our emotions from our thoughts.....and practise that enough, so we can when it is the HARDEST to do so.
Therapy, any therapy.........is just trying to help you give yourself permission to do so.
Whether you do this, cause you trust your doctor and he tells you to..........or you read it in a book or a post and it makes sense to you..........all these things, are just tools we use, to validate our own understanding.
It's amazing how much getting better, is about confidence. Confidence , in your own mind....
That is what you are seeking to build. There is more than one way to go about that. Just as there are many different types of therapys.....there are many different ways, to learn to get a bit better at controlling your mind.