I have thoughts like this a lot since I've gone to see a therapist. I think a lot of it can be made worse because of how society portrays mental illness as something that is completely incapacitating, and not that that level of extreme does not exist or is not experienced at some point with a lot of people with BPD, but just because you have good days doesn't mean what you are really feeling isn't valid. I grew up in a family that was always saying things like "you don't mean it", "it's just a phase", "you're not really this or that you're just acting like it, faking it" etc.. I think that's frustrating for a lot of us as we get older and need to recognize our feelings, it's easy to be dismissive of ourselves.