Why do I prefer to write songs when I'm sad rather than happy?

Forgive my English, I’ve been letting my brain flow carelessly, but yes, do I prefer being sad? Is there a meter in my brain that tells me I’m more inspired when I’m sad? When I’m happy I’m so carefree I just enjoy the moment and am not really tapped into a creative process. (I’m not ruling out that the latter can be applied, in my case it just doesn’t)

Strange…