What do spiders, snakes, and small spaces have in common with retirement? They're all among Americans' biggest fears, apparently. A study by Allianz concluded that a majority of U.S. adults aged between 44 and 75 are more scared of outliving their money in retirement than they are of dying.

Specifically, 61% of respondents said they feared running out of money more than death. And that number climbed to 82% among married people in their 40s with dependents. Respondents also admitted to other related fears, including not getting their full share of Social Security benefits and not being adequately prepared for retirement.

If you share those fears, the best remedy is to start saving whatever you can today. Maybe retirement is 30 years away for you, and that definitely works in your favor. But even if you're pushing 60 or older, the earlier you begin tucking cash away, the better off you'll be.

A young couple sitting on a couch looking at paperwork

Image source: Getty Images.

You can turn up at least $75 per month by making small changes to your spending habits. And that $75 monthly can grow into $100,000 or more over time. Here's how.

In a high-interest savings account

If you have 10 minutes to spare, you can open up a high-interest online savings account and schedule an automatic $75 monthly deposit. While this is a simple way to invest your cash, it's not the most fruitful. Even in a high-interest account, your interest rate will likely be between 1% and 2%, which will grow your total balance to about $9,800 after 10 years. The bulk of that money will be your actual deposits, but you will earn about $730 in interest.

The picture looks a little better if you keep saving for 30 years. In that case, your balance grows to about $34,000, including roughly $7,160 in earnings.

In a conservative, diversified portfolio

You could also invest your monthly savings in low-cost exchange-traded funds (ETFs) and low-cost mutual funds. Vanguard, Schwab, and iShares in particular have good index funds with low fees. Funds are ideal for a novice investor because they're professionally managed and diversified -- you don't have to research and pick stocks, and your risk is spread out among many companies. The advantage is that if one of those companies underperforms, it doesn't wipe out your gains.

In this scenario, you can target a modest return of 4% annually. If you achieve that, your $75 monthly grows to about $11,000 after 10 years. Stick it out for 30 years and your balance grows to more than $52,000.

In a more aggressive, diversified portfolio

If you have 20 years or more to save, you're in a great position to invest more aggressively. This is because the major stock indexes have historically shown returns of 9% to 11% in time periods longer than two decades.

Let's assume you have an advisor help you build a portfolio, and you keep depositing that $75 monthly to earn a 9% return over time. In 20 years, you'd have nearly $51,000 -- and about $33,000 of it would be earnings. Continue that trend for 10 more years and your balance grows to a whopping $139,440.

But here's a word of caution on working with a financial advisor: Pay attention to how they charge. Fee-only advisors charge flat fees for their services, while a fee-based advisor can earn commissions if you buy funds based on their recommendations. The fee-based structure gives the advisor an incentive to recommend assets that may not be suitable for you and your financial goals. 

In a more aggressive, diversified portfolio with company match

What if you have access to a 401(k) plan through work and your employer offers matching contributions? You can guess the answer -- your earnings skyrocket. If your company matches your $75 monthly contribution and the portfolio averages a 9% return, your balance in 30 years grows to nearly $280,000.

Your deposits into the 401(k) work differently than a standard transfer of funds into a savings account, and in a good way. Typically, you state how much to contribute to your 401(k) as a percentage of your salary, and the money is deducted from your check before your payroll taxes are calculated.

There are two notable perks here. One, you pay less in taxes. And two, because you're contributing a percentage of your salary, the dollar amount of your 401(k) contribution automatically increases whenever you get a raise. Most plans also allow you to increase your stated percentage over time -- say by 1% per year. That can be an easy way to build up your savings over the long haul.

And, if your company offers matching contributions, you can really gain momentum. Matching contributions are usually capped at around 3% or 4% of your salary. This means that if you contribute 4% of your salary to your 401(k), your employer will deposit an equal amount. And again, the dollar amount of that matching contribution increases every time you get a raise. It's basically free money.

Start saving small today

And sure, $280,000 isn't enough to support a free-wheeling lifestyle in your golden years. But it is more than you have saved today, and that's a win. Remember, too, that your ability to save can change dramatically over the next 10 years. Maybe today you can only scrape up $75 a month, but you could commit to increasing that number by $20 every year, or even more if your earnings increase. That'll only help your nest egg grow faster.

You can avoid some of life's scary stuff -- like snakes -- but you don't have that option with retirement. Protect your future by putting away whatever you can today.