If you went into the downturn with 60% stocks and 40% bonds, and made no changes, your mix might now be around 50-50. That means you cut your exposure to stocks just as they have become more likely to rise. From 1970 to 2008, a starting balance of $100,000 that was 60% stocks and 40% bonds, and never rebalanced, would have grown to $2.9 million, according to Schwab Center for Financial Research. But that same portfolio rebalanced annually would have grown to $3.5 million. So take a look at what's happened to your investments and rebalance to your target mix right away. Repeat this exercise at least once a year; more often when the markets are unusually volatile. But take note: rebalancing assets in a taxable account can trigger a tax bill; you're better off redirecting new investments to reach your target mix. There is no such tax consideration in a 401(k) plan.