Your biggest money mistakes -- and how to avoid them

Buying on impulse

You run into the supermarket for milk and eggs and spend $55 on extras. Standing in line to pay for gas, you pick up a magazine and a soda. Sound familiar? You’re not alone.

Research from the Wharton School at the University of Pennsylvania found that 20% of purchases are unplanned. If the shopping trip itself is unplanned, the rate of impulse shopping goes up 23%.

The problem with shopping on impulse is that it foils attempts at sticking to a budget.

Smart move: Be prepared.

The best way to avoid impulse purchases, according to James A. Roberts, professor of marketing at Baylor University, is to leave your credit and debit cards behind when you go to the store.

"Using cash or checks to pay for your purchases (is) much more painful than using (plastic)," he says.

Roberts also suggests instituting a cooling-off period for any purchase over $50. Taking time to think about whether the item is a true necessity or just a shiny object that caught your eye will help you keep impulse spending in check.