It's difficult to plan for retirement, especially with all the uncertainty associated with your future money needs. But just correcting one misimpression can make it much easier for you to reach your retirement goals.

In the following video, Dan Caplinger, The Motley Fool's director of investment planning, looks critically at one common assumption: that you have to replace almost all of your pre-retirement income in order to sustain the standard of living you want. Dan notes that most professionals assume you'll need 75% to 85% of what you earned during your career. But he also points out for those who've traditionally saved much of their income, the more important metric is how much you spent during your career, not what you saved. Just making this one simple adjustment can cut hundreds of thousands of dollars from what you'll need to save, helping many attain a more realistic goal for their retirement savings in the long run.

Have general questions about Social Security? Email them to SocialSecurity@fool.com, and they might be the subject of a future video!