"UNLIKE PAYING DOWN credit-card debt or a mortgage, retirement planning is a lifelong pursuit. It begins in your 20s and extends far beyond the day you exit the workplace. As a result, figuring out how much money you'll need may seem like an impossible feat.

While saving up for retirement is difficult to begin with, it gets worse. Even if you diligently stash money away for decades, one investment misstep can mean the difference between a relaxing retirement filled with days playing golf on the back nine and one that requires you to slave away at a job for years longer than anticipated.

To secure your place on the golf course, here are five all-too-common retirement mistakes to avoid."