TOTALLY relate to this. I'm diagnosed BP as well as BPD (by some docs), but even before BPD turned from just traits into a real diagnosis, I was sensitive to rejection. Friendswood cancel on me or change our plans in a way that seemed malicious, I would get very upset. This was me just being irrational because I know that they did not mean any harm but in my head I was able to twist the facts so it seemed like I was a victim.
I as well can have a hard time with criticism, even if it's just constructive and as well not malicious at all. My emotions seem to just be intense, therefore I react intensely. Though some doctors think that I have BPD and have diagnosed me with it, I don't really think that I completely fit it because I'm not an impulsive person and therefore I don't get criticized very much. That's why I think I'm so sensitive to it as I'm not used to actually being criticized.
I hope I was able to help at least a little bit! You don't have to be BPD to have intense emotions - bipolar can too.