BlackRock CEO Larry Fink once told a story about having dinner with the investment manager of one of the world's largest sovereign-wealth funds. The fund's objectives, the manager said, were generational. "So how do you measure performance?" Fink asked.

"Quarterly," said the manager.

Even rational, level-headed investors probably check their portfolios too much. That can stress us out and give us a false sense of what "risk" truly is.

In this video, Fool analysts Morgan Housel and Matt Koppenheffer discuss how closely investors should follow their stocks.

Try any of our Foolish newsletter services free for 30 days. We Fools may not all hold the same opinions, but we all believe that considering a diverse range of insights makes us better investors. The Motley Fool has a disclosure policy.