401(k)s used to be a surefire way to save money for your future. But now, for the first time in 20 years, retirement accounts are losing money. Last year, 401(k) plans lost $72 billion, and it's estimated that the average account lost $48,000.

Financial adviser Ray Martin says investors are concerned, frustrated and angry, asking questions like: "How much have I lost?", "Why did this happen?", "Is there a problem with the fund I invested in?", "What should I do now?"

And here is the problem: People are doing nothing. People leave their jobs without managing their 401(k)s. People aren't investing in their IRAs. People are frozen or paralyzed. They haven't increased their savings. And with the market downturn, a lot of investors' mistakes are uncovered.

Remember: 401(k)s give you control, and along with control you have responsibility. It requires maintenance - you have to do something!

Here is some advice from Martin on how to maintain your 401(k):

1. Diversify - Stocks, Bonds and Cash
If you haven't worked out an allocation strategy, then you should do it now. Asset allocation is all about not putting your eggs in one basket. It's the ultimate protection should things go wrong in one investment class or sector, as is likely to be the case from time to time.

What this means is to decide on what portion of your investments will be in cash, bonds and stocks. Investors who plow all their money into stocks or stock funds are now reminded that while this can lead to higher returns in some years, the losses that can follow can wipe out the gains. An investor who allocated a portion of their portfolio in bonds were rewarded with 10 to 20 percent returns on that portion last year, while their stock investments fell.

If you haven't diversified your portfolio, do it now. There's no single "correct" mix of stocks and bonds. Either do this yourself or seek help from a financial adviser.

2. Re-balance your 401(k) yearly.
All investors should stick to a process of re-balancing their portfolios. Make sure the allocation strategy you have decided upon is maintained by taking some money from your investments that have grown out of proportion and re-investing that into the investments that are under-weighted. This process requires continuous attention and possibly taking action several times a year.

3. Save, save, save.
People are not saving as much as they should. Two thirds of your future retirement assets comes from saving properly. One third will come from investing. You should still contribute the maximum allowed to your 401(k) account, because it is one of the surest ways of boosting the value of your retirement savings.

4. Get advice.
Not sure what to do? You're not alone. Many people feel overwhelmed. It's OK not to understand, but get advice on line, or call your 401(k) company. Don't neglect this. Do it now.