Buying a monthly class card might seem like an easy way to get in shape—you can try yoga one month, Pilates the next, and you get a discount on the price of the classes for buying the card. You convince yourself it's cheaper to buy the class pack to save $2 or $3 per class than it is to pay as you go. But Ramit Sethi, author of I Will Teach You to Be Rich, says that people overestimate how much they'll exercise by up to 70 percent. So the 10 kickboxing classes you've convinced yourself you're going to? You'll probably make it to two or three of them—at which point that 30-day card won't look like such a hot deal.
The Solution: For one month, pay for each class you go to individually. If you end up going to 10 classes, then you'll know for sure that the class card is a good deal going forward. If you have a fabulous time at yoga...but only go twice, you might stick to paying on a per-class basis.