The tricky thing about airline upgrades, daily deal sites and other bargains is that they can make you crave luxuries you couldn't otherwise afford. Say you buy a voucher for a $50 haircut and color at a swanky downtown salon and hit it off with the stylist, so you decide to go back and pay full price. Now you're on the "hedonic treadmill," paying full price and returning every few weeks to touch up your roots without that boost in happiness you experienced initially.
"Understand that a treat is just that: a reward, something to appreciate, not something that has to be every day," says McGrigg. "If that salon is part of your regular way of living, it's not special anymore."