I remember somewhere reading a chart showing symptoms/characteristics of BP and of BPD. It listed fear of abandonment under BPD. Under BP it said something like high sensitivity to rejection. Though some may see those as the same, I don't. And I think it is an accurate assessment. It's true for me anyway.

People fall away all the time. Whatever. But rejection... To me that is something more day-to-day. Being regularly negated, dismissed, talked over like I'm not even there can really get me down. There is a feeling of not mattering, invisibility, and just plain that I've got no business participating. The outsider who just doesn't fit in.
And yes, when depressed, more negatively affected by it, because it only reverberates and "confirms" the validity of all the negative talk already in my head.

What to do? Actually, this happens to me a LOT at work. I try to remind myself that it is often a manifestation of their own issues (such as need to assert their superiority by putting others down to protect their tiny kingdoms and maintain their position in the social jungle) and really isn't about me.

So I tend to just basically keep thoughts to myself so as not to invite it. I can't change them. They actually lose out on a lot of good ideas. Oh well.

In other instances it has been more of an exclusionary thing-- the others clustering up, making social plans, gossip and jibber-jabber. I realized their activities were not of interest to me anyway (bar room and relationship drama, shopping etc.). So really the rejection was a blessing in disguise. Better to be myself than to be miserable trying to fit in.