If you’ve checked your retirement account recently, you probably liked what you saw.

Both the S&P 500 and the Dow Jones Industrial Average have posted double-digit returns over the past few months as part of a historic nine-year bull market run. 

Though it's tempting to get in on the action, the "market will take a breath at some point," says Robert Milnamow, president and chief investment officer of Barrett Asset Management, based in New York City. "A run like this has happened only once in the last 90 years—from 1991 to 1999."

The smart money says you should instead take this time to optimize the investments you already have and not focus on new ones. Reviewing your investments at least once a year is a wise idea, says John O'Meara, a New York City certifed financial planner and principal of Inner Harbor Advisors. Times like these are a good reminder to check in. 

Here are four things to do, and not do, right now.

Investment Moves to Make Now

DO: Play the long game. When the stock market goes up, it’s better news than when it’s on its way down, but the advice remains the same: Sit tight and stay focused on your long-term investing goals. Selling or buying investments based on how you feel about the market today is not only risky business—it sets you up to earn less over time.

Multiple studies have shown that investors who trade more frequently earn less on their investments than those who buy and hold investments that track a stock market index, like the S&P 500. According to one analysis, active investors earned 11.4 percent over a five-year period, much less than the 17.9 percent stock market return over the same time frame. Even Warren Buffett recommends that the average investor should put their money in an index fund that tracks the S&P 500.

DON’T: Invest based on what you read or see on TV. Reading a few optimistic news articles on a certain company or industry doesn’t mean you know enough to invest in it. Whether or not a stock does well depends on many factors, and making a trading decision without doing your due diligence is more akin to gambling than investing.

Rather than trying to get rich quick by picking stocks, focus on what you can do, like increasing the amount you’re contributing to your 401(k) or your IRA. “The biggest factor in a successful retirement—and one of the few you control—is how much you saved while working,” says O’Meara.

DO: Rebalance your portfolio. Anytime the market makes big moves, as it has in recent months, your investments are likely to get out of balance. This is because the market doesn’t move in unison—while some industries are doing extremely well, others may falter. To bring your portfolio back into balance, you have to readjust your investments from time to time.

Let’s say you’re invested in 70 percent US stocks and 30 percent international stocks. If the US stock market outperforms global stock markets, that proportion could skew to 85 percent and 15 percent respectively. When that happens, you need to sell some investments and buy others to bring your allocation back to your original mix. Same goes for your proportion of stocks and bonds as well.

When in doubt, ask a financial advisor for help or invest in a target-date mutual fund instead. Target-date mutual funds are widely available and take the guesswork out of rebalancing your portfolio by doing it for you. To choose the right option, project the timeline for your personal goals. If you plan to retire in 25 years, for example, select a target-date mutual fund that focuses on the year 2040 or 2045. This ensures you maintain the right amount of risk to achieve your investment goals.

DON’T: Panic if the market starts to go down. Inevitably, the market will go down at some point, and it’s normal to feel anxious when that happens. But no market decline is permanent, and if you can stick it out, the market will eventually go back up, as we’ve seen in recent years.

The stock market may be unpredictable, but in the long run it pays to invest. Since its inception, the S&P 500 has rewarded investors with an average annual return of 9 percent. However, it’s important to remember that very few years have a clean 9 percent return. That average is made up of big swings in both directions over time. To achieve your investment goals, you’ve got to stick with it through the good and the bad.