We’ve all heard the slogan, “Dance like no one’s watching.” It’s meant to be empowering—a call to let loose and express yourself without fear of judgment. But here’s the problem: it’s bad advice. Why?

It's easy to let your income get eaten up by your children's activities. If you don't prioritize your nest egg, you might end up cash-strapped in retirement. You might also have to turn to your adult ...