Stumbling on Happiness, by Harvard psychology professor Daniel Gilbert (son of Larry Gilbert of Chapel Hill), explores the phenomenon of happiness, with results that promise to be surprising. From the excerpt at Amazon:
Yours [your brain] is nexting right now. For example, at this moment you may be consciously thinking about the sentence you just read, or about the key ring in your pocket that is jammed uncomfortably against your thigh, or about whether the War of 1812 really deserves its own overture. Whatever you are thinking, your thoughts are surely about something other than the word with which this sentence will end. But even as you hear these very words echoing in your very head, and think whatever thoughts they inspire, your brain is using the word it is reading right now and the words it read just before to make a reasonable guess about the identity of the word it will read next, which is what allows you to read so fluently. Any brain that has been raised on a steady diet of film noir and cheap detective novels fully expects the word night to follow the phrase It was a dark and stormy, and thus when it does encounter the word night, it is especially well prepared to digest it. As long as your brain’s guess about the next word turns out to be right, you cruise along happily, left to right, left to right, turning black squiggles into ideas, scenes, characters, and concepts, blissfully unaware that your nexting brain is predicting the future of the sentence at a fantastic rate. It is only when your brain predicts badly that you suddenly feel avocado.
So happiness and optimism are more complicated than we might think. Turns out, so is pessimism, we learn in Scott McLemee's review of Pessimism: Philsophy, Ethic, Spirit, by Joshua Foa Dienstag.
"Optimism," writes Dienstag, "makes us perpetual enemies of those future moments that do not meet our expectations, which means all future moments. It is when we expect nothing from the future that we are free to experience it as it will be, rather than as a disappointment.
Related: Paul comes down in favor of happiness, while Kristina in the comments demonstrates that a good gripe can help you get a grip.