Don't flub your 401(k)

NEW YORK (CNNMoney.com) -- A lot of things in life are complicated. This isn't: You can make the most of your 401(k) without breaking a sweat or your take-home paycheck.

In fact, not making the most of your 401(k) could cause you to break into a sweat and decimate your take-home paycheck as you enter your 40s and 50s.

The 401(k) is turning 25 this week, and in its first quarter of life it has become the main retirement savings vehicle for many workers.

Roughly 47 million people today are active participants in a 401(k) plan versus just 21 million who are active participants in a traditional defined benefit pension, according to data from the Investment Company Institute.

As valuable as the plan can be to your long-term future, it pays to avoid making these 5 costly mistakes.