Believe it or not, the biggest risk to your financial security is to do nothing. It's the same with your body; while exercise has the potential to hurt you, sitting still just isn't a healthy alternative.

Another odd one. But it's possible that investors who refuse to assume some level of risk can lose in the long run. If, for example, you saved money diligently all your working years but insisted on investing in CDs, your savings may not have grown enough to surpass inflation and meet your needs.

Perhaps you invest faithfully for years, enjoying good returns from your investments. But when you stop to calculate your expenses, you find that you haven't been saving enough money to realistically meet your financial goals.

Investors who refuse to diversify are taking a gamble, regardless of what basket they're putting their eggs in. It's a careful balance, however, because too much diversification can also be risky. When investors chase varying products from year to year, their investment portfolios become a crazy quilt of holdings with no particular pattern. The risk here is usually underperformance, though most anything is possible.