With my BPD, I always thought of happiness as an asshole with their high-beams on. You're driving in the dark then suddenly, out of nowhere, some idiot with his high-beams on comes towards you. It's too much to handle. It's so bright it's throwing you off. You don't know how to deal with it and before you can even adjust to it, the idiot drives past you and the darkness returns.

I don't know if that made sense to anyone but me, but that's always how I looked at it. For myself personally, happiness is even scarier than the anger/depression I endure.