• While market declines during a sell-off can induce fears, experts say it's important you don't stray from your retirement goals.
• "Today you're getting to buy it at a discount," said Winnie Sun, co-founder and managing director of Sun Group Wealth Partners in Irvine, California. "It's better to buy things on sale than to buy at full price."

Picture this: You walk into a big grocery store and everything is deeply discounted, said Winnie Sun, co-founder and managing director of Sun Group Wealth Partners in Irvine, California.

"What would you buy that you know that your household would need for the future?" she said. "That could be like paper towels, it could be toilet paper, it could be things that you know that you're going to need long term."

It's smart to adopt a similar mindset when the stock market pulls back as it did Monday, said Sun, who is also a member of the CNBC Financial Advisor Council. Think of positions that you would like to add to your portfolio.

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The Dow Jones Industrial Average had dropped 2.6% to start the week, while the Nasdaq Composite lost 3.43% and the S&P 500 slid 3%. The blue-chip Dow and S&P 500 registered their biggest daily losses since September 2022.

"When the stock market pulls back at these levels, these are great opportunities to invest in core names or a quality portfolio that you always wanted," she said.

"Today you're getting to buy it at a discount," Sun said. "It's better to buy things on sale than to buy at full price."

'The biggest mistake' to avoid

While market declines can make investors nervous, experts say it's important you don't stray from your retirement goals. That means staying invested and keeping on schedule with regular contributions.

"Turning off your retirement contributions is really not the way to go, especially when the market gets volatile," said Clifford Cornell, certified financial planner and associate financial advisor at Bone Fide Wealth in New York City. 

"Find comfort in the fact that markets do recover," Cornell said. 

In fact, stocks picked up on Tuesday: The Dow was up 1.45% shortly before close, while the Nasdaq and S&P were up 1.84, and 1.83%, respectively.

"The biggest mistake," is when individuals sell off their assets during market downturns, according to CFP Stacy Francis, president and CEO of Francis Financial in New York City.

Then they "miss out on the wonderful rally that we're seeing today," said Francis, a CNBC FA Council member.

That's not an unusual pattern: In a JPMorgan Asset Management analysis spanning Jan. 1, 2003 to Dec. 31, 2022, seven of the market's 10 best days happened within two weeks of its worst 10 days.

Francis also cautioned that the market will likely continue to see volatility leading up to the presidential election.

"You can't control the market, but you can control how you react to that," Francis said. "How you react is going to spell your long term success."