"If you're using a beauty product to avoid a negative outcome, like looking more tired than you are, then negative feedback can actually encourage you to stick with the product," says Rana Sobh, PhD, assistant professor of marketing at Qatar University, who studied more than 200 women who had used various beauty treatments over the course of a year. She and her colleagues found that among those who felt the treatments weren't working, 73 percent wanted to continue using them. And among women who found the treatments successful? Fifty-five percent had fallen off the wagon. The researchers' theory: Just as failure fuels your fear (and keeps you buying refills), success mitigates anxiety and weakens your motivation to stick with your regimen. Even Sobh says she has fallen into these patterns: "I used to apply a very expensive eye cream religiously—until one day my sister said, 'I can't even see your wrinkles.' I immediately stopped using it...and started worrying about my neck. Now I know why."