I don't have BPD but I want to answer this question, lol.
I used to be a prolific liar to the point of it being daft, but at some point I learned to control the situations I'd lie in.
Nowadays I'm a lot more truthful, but I've still tended to use bending truths a little too far. Lying can be something I do have to rationalize if it isn't
really beneficial because its obviously stupid in some situations.
Bending the truth is easier to rationalize than outright lying. Something I figure I need to learn is that if it seems unclear what's "really the truth" its a sign of rationalization, and if I'm needing to rationalize what I'm communicating its a sign my mind is actually screaming out against doing it, i.e. on some level I know what I am doing is detrimental to me, but I'm also attempting to self-sabbotage.
i.e. while reading this question I've realised its much better to lie and be 100% clear about what you're doing than say anything at all when you're unclear on what you're doing and why. Stop.. walk away.. ask "am I trying to screw up my life again? and if so, why."
[Thought] "My life is over because of my medical record" > [reality] "I feel powerless to do what I really want with my life, I'll blame it on my medical record instead of trying to work around it".
Result of failing to recognise > self sabbotage - make medical record even worse, make fear manifest as truth. Doh.
No feeling sorry for myself - I screwed up, consequences are on me - shut up work on the issues I do have [clearly some to get going with.

] and get on with my life... its on me to learn to let go of issues/regret surrounding that.