One of the first conditions of happiness is that the link between Man and Nature shall not be broken.

Human beings are not built for rooms alone, and something goes flat when weeks pass without weather, sky or living things. It is not mysticism to notice it; most people can feel something settle after even a short spell outside. The link is easy to break without ever deciding to, one busy season at a time.

Repair is unspectacular. Eat one meal where you can see out, walk the long way, keep something growing on the sill. Frequency matters more than dose, and this is one of the few remedies that costs nothing.