The quest for happiness is back with a vengeance. The bookstore’s self-help section is overflowing. Colleges offer courses on happiness, and they are oversubscribed. Institutes that present “pleasant activity training” and “mindfulness training” and help you learn to increase your “flow” abound. Meanwhile, we all feel a bit serotonin-deprived and eagerly await the next mind-enhancing drug, a safe and legal version of Ecstasy.