Defying the polls and odds, Donald Trump won the presidential election. As the results became clear on the evening of Nov. 8, financial markets around the world reacted swiftly: Stocks plunged (at one point during the overnight session, U.S. futures were down 5 percent, indicating a more than 800 point wipeout for the Dow Jones industrial average), the Mexican peso cratered by 13 percent, the U.S. dollar tumbled and safe havens like gold, U.S. Treasury bonds and the Japanese yen jumped.

Then a strange thing happened: as Trump spoke in the wee hours after capturing enough Electoral College votes to win, markets started to reverse course, as investors seemed to take some comfort in his conciliatory tone. By the time they rang the opening bell on the day after the election, stocks had steadied and actually closed higher on the session.

So what happened over the course of 18 hours? In the short run, investors may have learned a lesson from the United Kingdom’s Brexit vote. After that unexpected outcome in June, U.S. stocks were down 5 percent in the subsequent two trading sessions, but then they slowly marched back up as investors concluded that it would take a long time to figure the impact of Britain’s departure from the European Union.

While investors had been concerned about some of candidate Trump’s campaign rhetoric on trade and immigration, in the immediate aftermath of the election, it was hard to measure the impact on the U.S. and global economies, as well as what future policies could mean for corporate earnings.

Still, hours after the results came in, I was inundated with reader/listener/viewer questions that went something like this: “What should I do with my retirement account?” The answer for long-term investors is clear: absolutely nothing!

Unexpected events can create market volatility — both to the upside and the downside, which can lure you into feeling like you should do something. Try to resist that urge by reminding yourself that you are not investing for the next four weeks, four months or even four years — you are trying to build your nest egg beyond those time frames. And even if you were planning on retiring at the end of this year, you aren’t likely to pull all of your money from your account at once — you need it to last for decades in the future. In other words, you are not investing to retirement; rather you are investing through retirement.

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That’s why you have created a diversified portfolio, based on your goals, risk tolerance and time horizon — because over the long term, this strategy works. Yes, the unknown is scary and can lead to market volatility, but you have to refrain from being reactive to short-term market conditions. It’s not easy to do, but sometimes the best action is no action.

If you were freaked out when you saw big numbers on the downside, maybe your portfolio has too much risk. If that’s the case, you may need to readjust your allocation to better align with your risk tolerance. If you do make changes, be careful not to jump back into those riskier holdings after markets stabilize. Conversely, if you were kicking yourself for not being fully invested as stocks swung back to the upside, you might need to hold your nose and get back in.

One last note: battling emotions is something every investor encounters. One way to help you out is to establish auto rebalancing for your accounts, which can help take fear and anxiety out of the investment process.

Jill Schlesinger, a certified financial planner, is a CBS News business analyst. She welcomes emailed comments and questions.