For an investor to succeed over time, they need to buy low/sell high. This is obviously not easy as no one can predict the future. What you can do is to look for opportunities to buy low/sell high when they occur. This could be part of an asset allocation program, in which an investor looks to buy a company after a sell-off, after thorough due diligence is conducted and the investor believes in the long-term potential of the company. While it’s not easy to buy low/sell high, it is the goal for the long-term investor.