Just as many investors overreacted to the market on the way down, they need to keep a level head and not load up on too much stock in the current market rally, Vanguard is reminding investors in an online message from Chief Investment Officer Gus Sauter.

Sauter says that while “cautious optimism” and “measured confidence” are welcome due to the S&P 500’s 50%-plus rise from where it stood at the bottom in March, “we’ve all learned a valuable lesson during the past year, and that’s that market performance can certainly change quickly—for the better or for worse—with little or no warning.”

The company is encouraging investors to “maintain a balanced, well-diversified portfolio in a sensible way to prepare for the uncertainties and volatility that accompany investing in the stock and bond markets.”

Subscribe Now

Access to premium content including in-depth coverage of mutual funds, hedge funds, 401(K)s, 529 plans, and more.

3-Week Free Trial

Insight and analysis into the management, marketing, operations and technology of the asset management industry.