My good friend Dennis, a Seattle-based TV studio producer, pulled me aside Monday after I’d wrapped up Monday’s appearance on FOX Business Network‘s “Varney & Co.” to voice a sentiment I hear a lot these days:

…I’m almost 60 and scared to death by what’s happening today – terrorists, a looming rate hike, slowing earnings, global growth cratering.

He rattled off half a dozen items bugging him, counting each on his fingers. Then he leaned in and quietly said…

…it makes me want to sell it all.

If you’re like Dennis, you’re not alone.

Investors pulled almost $40 billion from the stock market last quarter alone, according to Morningstar. That’s nearly 50% of everything taken out for all of 2015.

But here’s the thing… no matter how grim the global situation is or even becomes, indiscriminately selling is exactly what you don’t want to do.

It’s one of the worst possible decisions any investor can make and, ultimately, one that will cost investors billions in lost profits.

Today we’re going to talk about why and, because this is not a simple subject, I’m going to prove it to you, too.

Roller Coaster Stock Markets DON’T Have to Mean Roller Coaster Returns

We’ve talked many times about the importance of buying low and selling high. It’s the path to higher returns.

So why is it that so many investors get it wrong?

The answer comes down to a phenomenon known as “recency bias.” That’s what they call it when investors make decisions based on what they see in the rear-view mirror. If the markets are going up, they buy. If they’re going down, they sell.

Simply put, they base their expectations for what’s next on what just happened. That’s like trying to bet which t-shirt a three-year-old will wear tomorrow, and about as successful.

In fact, there’s very little correlation between past stock market returns and actual future returns.