From the Wall Street Journal:
Joe Mansueto, chief executive of financial research firm Morningstar
An investor should think like a business owner, not a renter. Most businesspeople don’t get up in the morning and ask whether they should sell their business that day. If they own a pizza shop, they don’t think about whether what they really should own is a shoe store instead. They show patience and persistence and try to understand their underlying business better so they can earn the greatest return for the longest period of time.
So investors are in many ways misled by stock-market volatility. The values of the underlying businesses just don’t change as quickly as stock prices do. You really don’t have to watch those changes hawklike day after day.
It is in a lot of people’s interests to get you to do something. Advisers and brokers earn commissions, fund companies want you to bring your assets to them. There are a lot of forces at work in the investment industry to get people to move, and there’s not really a countervailing force to encourage you to do nothing. But you should.