It's from a lifetime probably of people telling you to calm down, shut up, or control yourself. I think that's the deal in my case. Or was. Now I don't care.
And funnily enough, I was CRAZIER when I thought being the opposite of me was right. I went from one extreme to the other, including trying to change myself for a couple of years, and being entirely miserable in attempts to repress myself or make myself something I'm not, I have found a balance.