Hello Eeeeeeyore: I've never been diagnosed as having BPD (although I have thought there was a time, when I was young, I might have been.) So I'm not really one of the members you're looking for here on PC. However I noticed this is your first post. So... welcome to Psych Central.

What I can say, with regard to your post, is that when I'm tired or not feeling well my own mental health struggles amplify quickly. And even though I know this is the case, that doesn't necessarily translate into me being able to short circuit the effects. So as for your family saying you become a nightmare when you're unwell, sometimes I think family members can be somewhat... shall we say... oversensitive? But certainly it seems reasonable to me to think you probably have a more difficult time controlling your BPD symptoms when you feel unwell.

Here are links to 5 articles, from Psych Central's archives, on the subject of BPD:

Borderline Personality Disorder: Symptoms & Treatments

Living with Borderline Personality Disorder

6 Gifts of Borderline Personality Disorder

7 Gifts of Borderline Personality Disorder | The Exhausted Woman

Dialectical Behavior Therapy in the Treatment of Borderline Personality Disorder

I hope you find PC to be of benefit.