I've had an S&P 500 Index Roth IRA open for 2 years that I consistently contribute at least 15% take-home to. It is set to reinvest any dividends. Over the 2 years, I've lost over 9%. I'm worried the current market is "robbing" future earnings. Should I reconsider my retirement plan? --Matt Brasher, 27, Atlanta

First off, congratulations for starting early.

Saving for something that isn't likely to happen for nearly four decades can be difficult, but investing for retirement early in a career puts time on your side and can make it easier to weather market downturns.

But let's face it: It's hard to stomach Wall Street's wild swings.

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"It's very easy to get distracted, concerned or agitated over short-term volatility with low or negative returns," said Scott Mazuzan, a certified financial planner with F.L Putnam Investment Management Company.

No one likes to watch their hard-earned money lose value, but an important aspect to investing is taking the emotion out of it to avoid knee-jerk decisions.

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"What successful investors learn is to not try and time the market ... it doesn't work," said Steve Martin, a certified financial planner and senior managing advisor at BKD Wealth Advisors.

A 9% hit might hurt now, but it helps to look at the bigger picture: In the last five years, the S&P 500 is up 60% and it's nearly tripled since March 2009.

And there is a silver lining for young investors. "Dips in the market mean you are buying cheaper," Martin pointed out. "For people in the accumulation phase, market downturns aren't always bad. You are buying more at lower costs."

Financial planners tend to recommend young savers keep the majority of their retirement funds in stocks since their time horizon is longer, but diversification is key.

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While the S&P 500 is a good barometer of the stock market, the experts suggested investing beyond the large U.S. companies that make up the index.

International stocks could help round out a stock portfolio, said Martin, who pointed out that more than half of global economic growth comes from other countries.

"That means over half of all opportunity is outside the U.S. Companies like Toyota (TM), Mitsubishi, Nestle -- big companies you use every day that you don't own with the S&P 500."

Adding small or mid-sized companies can also help balance out a portfolio, added Mazuzan.

It's important for investors of every age to know their risk tolerance and be comfortable with their investment strategy. For example, older Millennials or those with a lower risk tolerance could consider adding more bonds to help cushion the blow of any market turmoil. Bonds are considered less volatile than stocks. Just keep in mind that your bond values fall when interest rates rise.

"If you have a more diversified portfolio, when the market has these corrections, you don't have as much loss and you have a higher tendency to stick with it," said Martin.

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