I seriously think I may be hypomanic. This first occurred to me when my father was discussing his overstimulus and the fact that he is so energetic, sometimes, even in the middle of the night is unable to sleep, though he's very tired. And it registered that I have these exact symptoms. I try and cope by using coffee. He also said that he's always thinking, just as I do, my brain never winds down.
Here is the medical dictionary's definition:
Hypomania: A condition similar to mania but less severe. The symptoms are similar with elevated mood, increased activity, decreased need for sleep, grandiosity, racing thoughts, and the like. However, hypomanic episodes differ in that they do not cause significant distress or impair one's work, family, or social life in an obvious way while manic episodes do.
Hypomanic people tend to be unusually cheerful, have more than ample energy, and need little sleep. Hypomania is a pleasurable state. It may confer a heightened sense of creativity and power. However, hypomania can subtly impair a person's judgment. Too much confidence can conceal the consequences of decisions.