If you're imagining that once you wave goodbye to your pointy-headed boss and head off into the sunset, you'll live out the rest of your life in blissful retirement, think again. That's not how it's working for many people. It turns out that many people are returning to the workforce after retiring -- some by choice, some not. Heck, even a 67-year-old woman in Spain recently gave birth to twins: Our 60s are not turning out to be like our parents' 60s.