U.S. News (May 25, 2018) --Be disciplined, tune out the markets and if you make a mistake, fix it and move on.

AFTER HOURS OF deliberation, you did it: You shelled out $200 for a new pair of Nikes (ticker: NKE) But now that you're home, they just don't look or feel the same as they did in the store, and you're beginning to think you never should have bought them in the first place.

Sound familiar? Buyer's remorse is real, but it's not limited to shoppers. Investors feel remorse, too. 

"Anybody who's been in the market for any length of time has probably experienced investor's remorse," says Franklin White, senior vice president at PNC Wealth Management. And anyone who claims otherwise, "isn't giving you a straight story." The question for investors is how to avoid investor's remorse, and what should they do about it if they have it.

[See: 7 Things That Can Derail Your Retirement.]

Base portfolio changes on your circumstances, not the markets. Whatever portfolio change you made – or didn't make – that you regret, it was probably emotionally driven. "A lot of investor's remorse comes from individuals making emotional decisions rather than rational ones," says Michelle Brownstein, vice president of private client services at Personal Capital.

Our emotions are often highest when we're watching the news. "It's difficult to ignore the siren song of daily commentaries and events," says John Tyers, head of private wealth management at Citizens Bank.

But blocking out the market noise is key to making better investing decisions. "By not being susceptible to the gyrations of the market, you can avoid the risk of doing the wrong thing at the wrong time," says Ric Edelman, founder and executive chairman of Edelman Financial Services in Fairfax, Virginia.

The best way to accomplish this is to shift your allocations only when your life circumstances change, Brownstein says. Your long-term goals don't change based on market news, so neither should your portfolio.

Reconsider your portfolio risk. Often, an emotional or knee-jerk reaction is about something more fundamental – an investment strategy that doesn't line up with risk tolerance, Brownstein says. For instance, if your latest investment gaffe was to sell too soon, you were probably taking on too much risk. To prevent a similar occurrence in the future, she suggests reallocating that cash into a more moderate portfolio. 

With an appropriate investment strategy, you'll be less tempted to sell on market down days or make the kind of changes that ultimately lead to investor's remorse.

"Investors sometimes feel remorse when they make investment decisions that don't immediately produce results," Tyers says. "But investing isn't gambling." It's a long-term play. So keep your eye on the future and "don't sweat the small stuff," he says.

As long as a portfolio change reflects your long-term financial goals, it doesn't matter what happens right out of the gate. Instead of obsessing over short-term results, focus on building a solid plan that can weather any day-to-day volatility. 

[See: 13 Ways to Take the Emotions Out of Investing.]

If you've made a mistake, fix it. Ultimately, "the best way to avoid regret is to never look backwards," Edelman says. We make the best decisions we can with the information we have at the time. Tomorrow may present new details that contradict today's information, but "don't punish yourself for making the best decision you could based on the available information," he says.

That said, if you've made a mistake, correct it. The longer you wait to correct a bad investing decision, the more severe the consequences may become.

"Don't set up trigger prices or wait for a particular economic or market event" to take action, White says. Trying to time the market can exacerbate emotional decision-making and can lead to more losses or missed returns while you sit on the sidelines. "Make a plan for getting your portfolio back to where it should be expeditiously, without considering the markets," White says. 

This doesn't necessarily mean selling or buying back in right away. "Selling a position that's lost value permanently impairs your capital and limits future investment opportunities," says Bill Tait, financial advisor at Essex Financial in Essex, Connecticut.

For a position bought in error, the fix depends on what the investment has done since you bought it, he says. If it "hasn't moved much, the loss may be minimal and exiting in a timely fashion can provide peace of mind." If the stock has lost value but you see no fundamental problems with the company, he recommends holding it for a full market cycle.

But if a material change to your situation renders an investment a poor fit for your portfolio, sell it, White says. Likewise, only rebuy the investment if the position suits your long-term goals. 

Don't be afraid to ask for help. "One of the biggest reasons investors choose to work with advisors is because delegation takes the emotion out of decision-making," Brownstein says. "If you tend to make emotional decisions, delegating can be the smartest thing you can do."

With one caveat, she says: Make sure you work with a fiduciary, who is legally required to act in your best interest, and not a broker or dealer, who is not.

In extreme cases of severe financial harm, you might want guidance of another nature. A lawsuit may be prudent because the person who sold you the investment may have committed a crime, Edelman says.

If you want to file a lawsuit against a financial professional, start by consulting the Public Investors Arbitration Bar Association (PIABA), an international association of attorneys who represent investors in securities industry disputes. PIABA can connect you with a qualified attorney in your area.

[See: The Fastest Ways to Lose Money in the Stock Market.]

The Financial Industry Regulatory Authority also "has an arbitration process that's cheaper and faster than a lawsuit," Edelman says. And the Securities and Exchange Commission takes action against people who commit financial crimes like Ponzi schemes.