What does cheerful and buoyant mean?

You yourself belong to the brighter country in the yellow light, and so, at all normal times, you are buoyant, cheerful. 

Whenever you get low in your mind, it is always the result of a depressant from without, and at such times, you should go away somewhere, and stay for hours. 

You would be better at the park―or out of town, as many hours a day, as possible.