Many women are neck-deep in career-building during this decade. The unhappy side effect? Killer work stress. Get off the hamster wheel by avoiding automatic �yes� responses to requests that catch you off guard, says Gretchen Rubin, author of The Happiness Project, a book chronicling the year that Rubin spent test-driving scientific research and popular wisdom about how to be happy. If saying �yes� makes sense, fine, but being choosy helps you avoid the powerless feeling that leads to burnout.