9 reasons you overspend

You’re counting calories

On a diet? Keep an eye on your wallet.

It appears that self-control is a limited resource, which means you’ll be able to resist chocolate cake but not the strappy sandals at the mall. (This also works in reverse: You may have the self-control to keep your credit card in your wallet in the shoe store but not in the food court).

“There's only so much sacrifice and stress a person can handle,” Yarrow says. “To make matters worse, dieting and ‘sacrifice’ in one area sets us up for rationalization in other areas, such as, ‘I've been so good on my diet, I will reward myself with this new pair of shoes.’ ”

Dieting can also blow the budget, because healthy eating costs more. Skipping processed foods and stocking up on fruits, veggies and whole grains may help whittle your waistline, but it’ll bulk up your grocery bill. In one study, researchers found those with the healthiest diets spent 24% more on groceries.

Smart move: If you’re trying to slim down, avoiding temptation is the best strategy, Yarrow says. So steer clear of scenarios where you’re likely to reward yourself with strappy sandals or a techie gadget for sticking with your diet.