This seems true to me. When I'm manic I have lots and lots of energy and everything I do is just faster. When I'm experiencing mania or hypomania I am often happy, but not always. Sometimes I'm irritable or even feel hopeless. So it seems to be more about energy than mood for me. With depression, on the other hand, I'm always slowed down AND sad. This is a complex illness, and although I'm just now starting to learn more about it, it seems to manifest slightly differently in each person. I think there's a lot of individual variation.