Once you retire, the goal is to make your money last as long as possible. So now, instead of making sure your investments are in line with your original plan, participants typically make the shift to a more conservative investment strategy to reduce the risk of loss.
Investment types, like CDs, money market accounts, bonds and guaranteed income funds can help protect your money and better ensure (but not guarantee) your future income will be there. And not be exposed to the risk a fluctuating market can bring.
Work with a financial professional to learn about the importance of being a little more conservative and helping protect your retirement.