Since many investors love to talk and focus on share price, then I shall divert my explanation on share price. As long as the share price decline is not due to the poor performance of the company, weakening fundamentals, or the sudden existence of a new risk, the share price will bounce back over time for great companies.

Whenever this happens, it's time to buy more to average down or average up. You can either let emotions run your decisions or use common sense and logic to think. If you bought a very good company but keep on fearing and cannot stand looking at the increasing "losses," by all means sell at your own peril.

As for me, I use the company's fundamentals as an anchor to make my decisions and judge a company's performance, not the share price. All we need is time and patience for the market participants to wake up to reality and realise the true potential of the company. When the time comes, the fundamentals of the company will pull the share price towards its true value.