It may seem that way, but that's not the way it actually is. Some people here still haven't accepted the dx fully-I still question it at times, despite the fact that 3 pdocs all agree that I have bp II. A lot of people take years to fully accept that they have bp (or any mental illness), to the point where their treatment is delayed. Many people on this board were misdiagnosed and misdiagnosed before someone finally discovered that they had bipolar ...so as confident as we may seem with our diagnoses, none of us just 100% knew we were bipolar as soon as we started having symptoms.

It can be really hard to distinguish bipolar from BPD. I don't know (and would love to know, so if anyone has this information, tell me) if BPD mood swings can cause euphoria, or if BPD mood shifts are just between depression, irritability, and anxiety. if BPD can include brief periods of high mood, then maybe you only have BPD. If BPD doesn't include periods of elevated mood, or if your highs are a lot more intense than the average borderline's highs, then perhaps you should continue to explore bipolar a little more. My hypomanic mood is a bit above simple happiness; I feel elated, like my entire body is charged with this wonderful energy. I doubt that a normal person could feel that good without drugs. And my hypomanias are relatively mild! So someone who describes hypomania as just "normal" or "happy" may either have been misdiagnosed, or not have a full grasp on what normal happiness feels like because his/her mood has been very dysregulated for a very long time.

Dr. Phelps is a psychiatrist who specializes in bipolar II, and his wonderful website helped me to start to accept my diagnosis. He has even written an article on the differences between BPD and bipolar: http://www.psycheducation.org/depression/borderline.htm

There are several scientifically validated bipolar quizzes out there, but many (most notoriously the Mood Disorders Questionnaire, which pdocs often use in assessment) will give someone with BPD a positive screen because of shared symptoms, like impulsivity and mood swings.

I hope something here helps. Good luck sorting this all out; it's a difficult process!