The scary thing about investing in stocks is that the market could crash at any time, and it's hard to predict when. Over the past few weeks, stocks have been volatile, and things could get worse before they improve.

In fact, recent data from Allianz Life Insurance confirms that stock market jitters aren't uncommon. In a September survey, 54% of respondents worry that a big stock market crash is just around the corner.

Not only that, but 36% say that recent volatility has them worried about their retirement accounts. And 67% say they're keeping at least some of their money out of the stock market to protect themselves from losses.

Person looking at laptop screen.

Image source: Getty Images.

If you're concerned that a stock market downturn is near, you're clearly in good company. But rather than lie awake at night worrying, here are a few things you can do to prepare.

1. Assess your current holdings

If your portfolio isn't diverse, you may want to make some changes before things get worse. (To be clear, we don't know that they will get worse, but it's a possibility.) If you're overloaded with stocks from one particular market segment, now may be the time to shift things around so you're invested across a range of segments instead.

You may want to consider buying some S&P 500 ETFs for added diversification. And you may want to look outside of stocks. Real estate investment trusts (REITs) are a good bet in this regard because they don't always move in sync with the stock market.

2. Make sure your retirement portfolio is age-appropriate

If you're in your 30s or 40s with plans to retire in your 60s or 70s, then there's really no need to worry about a near-term stock market crash, because ideally, you won't be tapping your retirement plan for many years. Even if stocks do tumble in the near term, you'll have plenty of time to sit back and wait for them to recover.

But if you're only a year or two away from retirement, now's the time to review your IRA or 401(k) plan and make sure it's invested appropriately, given your age. For the most part, that means you shouldn't be overwhelmingly invested in stocks. Rather, you should aim for more of an even stock-bond split if you think you'll be taking withdrawals from your savings within a year or two.

3. Stockpile some cash

Some investors think of stock market crashes as negative events. Others see them as opportunities. And if you do your part to sock away some extra money in the bank, you, too, can take advantage of the chance to buy quality stocks once they go on sale.

It's also important to have cash reserves on hand so you aren't forced to tap your portfolio when a need for money arises. If you liquidate investments during a stock market crash, you may end up locking in losses that are difficult to recover from.

Keep calm

We don't know when the stock market will take a serious turn for the worse. It could happen in October or it may not happen for months or even years.

The best thing you can do at this time is get yourself into good shape to ride out a downturn. That could mean diversifying more in your brokerage account, shifting assets around in your retirement plan, or simply loading up on more cash so it's there when you need it.

Either way, do your best to stay calm in the face of a potential crash. The stock market has a long history of recovering from downturns, and there's no reason to think it's lost that ability.