It's hard to truly relax between rages--I know that "waiting for the next approach" feeling all too well. There are ways to deal with the rages and protect yourself, and sometimes when things are quiet, that's the best time to really read up on BPD and practice the tools that can help you deal with the rages.
It is my responsibility to somehow stop this internal anxiety... .
It is, but you don't need to do it alone. There are excellent tools and resources that can help you work on that internal anxiety. What have you tried so far? Are you still in counseling? Therapy, along with what I've learned here and through a lot of reading, has really helped me to calm that anxiety.