Investors, it is often said, are driven by fear and greed. At a time like this, I’d add a third item to that list: regret. The past 18 months have been enough of a roller coaster to give even the most even-keeled investor a stomach ache and have created ample opportunity for regret. Since the fall of 2018, the stock market has dropped 20%, then gained 30%, then dropped 35%, then gained back 30% again.

As a result, these are some of the sentiments I’ve been hearing over the past month:

• “Why didn’t I sell at the top?”
• “Why didn’t I buy at the bottom?”
• “Why did I bother buying international stocks?”
• “Why did I buy high yield bonds?”
• “For the love of God, why didn’t I ever buy a single share of Amazon?”

None of these reactions is surprising—but it’s worth asking if regret like this serves a purpose. There are two schools of thought on this question. Nietzsche famously said that, “remorse would simply mean adding to the first act of stupidity a second.” In other words, don’t waste any time looking back. But the other school of thought sees a lot of value in looking back. That’s because it allows us to reflect on our decisions and to think about what we might do differently next time.

I see logic in both philosophies, but what’s most important at times like this is simply to be aware of the power of emotions and of the unhelpful tricks our minds can play on us. To help manage the stress, and to help make the best decisions going forward, here are some other key concepts from behavioral finance that are worth keeping in mind:

Loss aversion. In behavioral finance, probably the most famous concept is something called prospect theory. In short, what the research has found is that people hate losses, and we hate them disproportionately to the happiness we derive from gains. In fact, people dislike losses about twice as much as they enjoy gains of a comparable size. That’s especially important this year. Since the market peaked in mid-February, the S&P 500 is down about 13%. But as of yesterday, the stock market was slightly higher than it was a year earlier. Because of our natural loss aversion, though, it feels much worse than that. It’s very hard to fight this instinct. The most valuable strategy, in my view, is to maintain perspective. When you consult historical charts, it’s much easier to tune out the hyperbolic-sounding headlines and to focus on where you really stand.

Rumination. Our minds are prone to rumination, considering and reconsidering what we might have done differently. For the most part, this isn’t productive since the past can’t be changed. But to put these ruminations to productive use, I recommend translating your thoughts about the past into specific plans for the future. If some aspect of your investment portfolio hasn’t behaved as expected this year, then spend time researching that particular investment and consider updating your investment strategy. Many people, for example, are re-examining their bond portfolios. Others are reconsidering the composition of their stock portfolios because of the weakness of traditionally “defensive” stocks such as utilities and the surprising strength of seemingly risky technology stocks. To the extent that there is a silver lining in all this, it is the opportunity to learn and thus to better prepare for next time.

The break-even effect. While there should be a difference between gambling and stock market investing, some of the same behaviors can be seen across both domains. One of them is called the break-even effect. What researchers have found is that gamblers who suffer losses in the morning will often make riskier bets in the afternoon in an effort to recoup their gains. The same thing has been observed among investors, and this is another bias to be aware of. The solution? Fortunately, unlike a gambler, you don’t need to take any action to restore the value of your portfolio. Once this crisis passes, there is every reason to expect that the market will recover. It may take some time, but if you believe that the economy will eventually heal, then there is no need to turn up the risk level in your portfolio to break even. It will happen on its own.

The brother-in-law effect. There will always be someone in your life who profited—or will claim to have profited—from whatever investment looks the smartest on any given day. These days, that would probably be Zoom or Teladoc. But just as you should tune out the headlines, you should tune out your brother-in-law or know-it-all neighbor. Research clearly shows that you’ll be better off that way.