If you think you're doing yourself a favor by hoarding your credit card rewards, think again. While it's commendable that you're saving for those airline tickets to Tahiti, a 2011 study from Colloquy.com found that the average consumer ultimately doesn't redeem a third of his rewards-or about $205 every year.
Your rewards are only rewarding if you have a concrete plan in place to spend them. Otherwise, they're just building up bit by bit, but you'll wind up leaving money on the table if you cancel your card, let your points or miles expire, miss a payment, or the company changes its program altogether.
Plus, if you get cash-back rewards, you can redeem them monthly and apply that small sum to your credit card balance, freeing up your own hard-earned cash to use on something you really need. They can also be a good way to start (or bulk up) your emergency fund. Unused cash rewards don't earn interest, which is why you're basically wasting money by just letting them sit.
If you don't understand the nuances of your rewards program, give your credit card company a call and ask them to explain it to you. Otherwise, set a goal to use your rewards in the near future, before they slip down the drain.