Tim Harford investigates the field of "happynomics" through which economists attempt to devise policies that make people happier, and does an excellent job of sorting the evidence-based approaches from the trendy rubbish that's part ideology and part wishful thinking. Bottom line: beware the "focusing illusion"; count your blessings to reverse your habituation to the good things in life; set things up so that doing the things you want is easier than doing the things that make you unhappy, and, finally, understand that you probably can't be happy all the time.
If this stuff interests you, I strongly recommend Stumbling on Happiness, an excellent book about the state of psychiatric research into happiness by Daniel Gilbert, head of Harvard's psych department.
The focusing illusion was splendidly captured by a pair of questions asked of college students by researcher Norbert Schwartz and others: "How happy are you?" and "How many dates did you have last month?" The research team discovered that people having a lot of dates also say they're feeling very happy – but only if asked about the dates first. If the happiness question comes first, there's a far smaller correlation between the answers. Those students asked initially about their love lives continued to think about them when pondering their happiness. Otherwise they might have been worrying about money, career or exams.
The focusing illusion lies in wait for us whenever we make a decision. Nattavudh "Nick" Powdthavee, an economist and author of The Happiness Equation, says that we have to try to "look beyond what's salient about an experience". Don't just think about the obvious when making decisions; think about how day-to-day life is likely to change as a result – if it changes at all.
(Image: Happiness / 20100117.7D.02031.P1.L1.BW / SML, See-ming Lee, CC-BY-SA)