Big moves in the markets can mean big changes in your 401(k), even if you don't do anything.  Most financial advisors will tell you not to try to "time" the stock market in your retirement account. But if you just "set-it and forget it," your 401(k) can makes moves on its own.  For example, when the stock market surges, your retirement portfolio can wind up with a larger proportion of equities than you planned for and expose you to an uncomfortably high level of risk.

In this CNBC.com web-only Reporter's Notebook conversation with Managing Editor Tyler Mathisen, our Personal Finance Correspondent Sharon Epperson recommends that you check the balance of your 401(k)'s holdings, something that should be done periodically even when Wall Street isn't riding a roller coaster. So, if you had previously decided to have 65% of your 401(k) in stocks and 35% in bonds, based on your goals and risk tolernance, you should look to see if that's what you have now. Sharon notes that some retirement plans feature automatic rebalancing.