Whenever there is turmoil in the markets, my phone lights up with calls from journalists, investors and potential clients. They are typically in a panic about the crisis of the moment and are calling for my take on the situation. In my decades as an investor and analyst on Wall Street, I have learned that panics come and go. They turn out not to be the main cause of investors’ financial setbacks. Rather, what hurts most investors most is a failure to understand the basics of investing. Not grasping the simple mathematical drivers of returns invariably leads to very costly errors. The best time to make an investment plan is before a crisis, not during it. When the sky turns cloudy, you should follow your plan, including all “exit strategies.” Consider these 10 points in the context of your own discretionary investments, 401(k)s and IRAs. Identify any errors you are making, and fix them now — before the next storm hits.