7. Bargains aren't always a bargain

Who can resist an offer like “buy five, get one free,” or “three for $1”? Apparently, very few people can. “Any time you see numbers in a sign, you’re likely to buy at least 30 percent more than you may have purchased otherwise. “So if you go looking for soup and the sign says “limit 12 per person,” chances are you’ll purchase several more cans than you intended to buy,” he says. And of course, if you buy more than you need, it’s not necessarily a bargain. Or worse yet, it could lead to over-indulging. “Mindless shopping leads to mindless eating,” says Wansink. “Once the stuff is in the house, you’ll eat it whether you really want it or not.”