Your individual goals and financial capabilities influence your decisions regarding proper management of your investments. If you believe the stock market is poised for unacceptable declines and want to shield your portfolio from potential economic downturns, a shift to more conservative assets may suit you.
Similarly, as you approach the date when you expect to begin withdrawing money from your investment account, you may want to reduce your portfolio risk to better secure any gains you have earned. Fidelity Investments explains, "How you determine your asset allocation largely depends on your comfort with risk and the time frame for your investments."