According to a recent SoFi study, 56% of millennial women have money to invest but aren't doing so because of fear.

It's understandable to be worried about losing money in the market -- especially for a generation that got a firsthand view of the 2008 financial crisis -- but unfortunately, it's almost impossible to accomplish most financial goals without putting money into the stock market.

The good news: Investing doesn't have to be scary. It's not hard to build a pretty safe portfolio that stands a very strong chance of performing well over time.

Financial forms with a cup of coffee and pair of eyeglasses sitting on top

Image source: Getty Images.

Why you need to invest your money

Investing in the stock market is one of the key ways to build wealth, and it's something that you should start doing when you're as young as possible.

Historically, the stock market has outperformed both real estate and bonds. And in today's low-interest-rate climate, investing can be especially important; if you leave your money in bonds or in a high-yield savings account, the returns you'll earn will be paltry.

Vanguard estimated in 2018 that the 10-year Treasury yield will be around 2.5%, while its long-term projection for the stock market suggests about 4.5% to 6.5% expected returns over the next decade. While these are just projections, and historically both stocks and bonds have performed better than these projections indicate, there's one clear trend: Stocks outperform bonds by significant margins.

And this makes a big impact. This chart below shows how much money you'd end up with, if you invested various amounts at different rates of return from age 30 to age 65:

Annual Investment

2% Return

3% Return

4% Return

5% Return

6% Return

7% Return

8% Return

$1000

$49,994

$60,462

$73,654

$90,320

$111,434

$138,236

$172,316

$2000

$99,988

$120,924

$147,304

$180,640

$222,869

$276,473

$344,633

$3000

$149,983

$181,386

$200,956

$270,960

$334,304

$414,710

$516,950

$4000

$199,977

$241,848

$294,608

$361,281

$445,739

$552,947

$689,267

$5000

$249,972

$302,310

$368,261

$451,601

$557,173

$691,184

$861,584

$6000

$299,966

$362,772

$441,913

$541,921

$668,608

$829,421

$1,030,000

$7000

$349,961

$423,324

$515,565

$632,242

$780,043

$967,658

$1,210,000

Data source: Calculations by author.

Clearly, you need to put at least some of your money into investments that are likely to earn much more than bonds would. If you don't, you're unlikely to have enough for a secure retirement, even if you invest a pretty substantial sum of money each year.

How to get started investing

Investing seems scary because it's hard to pick investments, and there's undoubtedly a risk of losing money.

But the key is to invest for the long term in a diversified portfolio so if some assets perform poorly, others do well. The power of long-term investing is such that even when the stock market goes through down years, most investors who stay the course will recover quickly and stand the best chance of building real wealth.

You also need to make certain that you don't put all your eggs in one basket, which is why diversification is so important. Fortunately, there are very easy ways to diversify your investments.

One option is to use a robo-advisor such as Wealthfront or Betterment, each of which asks about your age, goals, and risk profile and makes investments for you. Robo-advisors, however, charge fees to manage your money, and fees can eat into your investment gains.

Another solution is to invest in exchange-traded funds (ETFs), which make diversification easy. These funds can be traded just like stocks, and many are commission-free with very low investment costs.

ETFs can give you exposure to a broad range of assets. You could, for example, buy a single ETF such as the Vanguard Total Stock Market ETF, which tracks the entire U.S. stock market. To achieve a truly diversified portfolio, you should also invest in ETFs that give you exposure to small companies (small caps), to emerging markets, to real estate, and to bonds.

There are model portfolios you can use to determine which ETFs you should invest in to build a diversified portfolio, or you can research ETFs to find specific funds you believe will give you a good mix of different assets.

You can buy ETFs from any discount online broker, simply leave your money invested for decades, and watch it grow.

Don't be afraid of investing

Being afraid of investing is natural, but it can cost you your financial security; it's almost impossible to save enough money for a secure retirement unless you invest in the stock market. Foregoing the chance to make your money grow should be far scarier than picking stocks and diving in -- especially when robo-advisors and ETFs both make it so easy to build a balanced portfolio.

Christy Bieber has no position in any of the stocks mentioned. The Motley Fool has no position in any of the stocks mentioned. The Motley Fool has a disclosure policy.