There was a time when she had indulged in the hypothetical for hours a day, plotting the map that had led her here. But no life is a line, and hers was an uneven orbit around a dark star, a moth circling a dead bulb, searching for the light it once held.
Sometimes it bursts from your imagination fully formed, sometimes you absorb from nonfiction, sometimes you're able to imprint your own autobiographical experiences on a world you never yourself were a part of. A decent number of the one-liners in the title story originally came up in conversations with my girlfriend or my neighbor.
In my own work, humor is necessary, for the reasons stated above, but also because forbidding your characters silliness, absurdity, irony, and vulgarity forbids them aspects of the human experience every bit as universal as sorrow.
From personal experience, I completely agree that it is often easier to go for monotone sadness. When I was starting out, I wrote a gazillion short stories that ran the gamut of human suffering - drug addiction, child abuse, terminal illness, loved ones dying by all manner of misfortune, etc. In hindsight, it's clear that I mistook the power of the situation for the power of the story.
We all know to feel sympathy for those who've suffered from drug addiction, child abuse, and terminal illness, so the set up elicits an emotional response that the story itself very well may not earn. Energy generated by the fiction itself is likely to produce more light.