If you're struggling to save for the future, you're not alone. One in five Americans has no savings at all, a survey from Northwestern Mutual found, and money is the No. 1 source of stress among U.S. adults.

Regardless of what you're saving for -- retirement, your kids' college fund, the down payment on a house -- it's not easy to set aside money for those goals. This is especially true if you don't have much extra cash to spare. Approximately 20% of Americans spend more than they earn, a report from the FINRA Investor Education Foundation noted. Furthermore, an additional 36% of people spend roughly the same amount that they earn, meaning less than half of adults have cash to save at the end of the month.

Even if money is tight, that doesn't mean it's impossible to save; it just means you may need to make some lifestyle adjustments. You don't necessarily need to slash your budget to the bare bones to find money to put away, but there are a few common financial habits that could be doing more harm than good.

Broken piggy bank with coins falling out

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1. Not tracking your spending

Tracking how much you spend each month isn't the most exciting task, but it's the only way to tell whether you're overdoing it in certain areas of your budget. You may feel as if you're stretched to the limit financially, but it could be you're just spending more than you realize on unnecessary expenses.

Nowadays, tracking your expenses doesn't have to be difficult or time-consuming. There are several apps that can help you stay on top of it with minimal effort, and you can also set limits and create alerts for when you overspend in a certain category.

Once you know exactly how much you're spending each month and what it's for, it will give you a better idea of where you can make cuts to put more cash toward your savings. You also may not need to make drastic reductions to meet your savings goals. Sometimes, all it takes is cutting $10 or $20 per month across multiple categories to save a couple of hundred dollars per month.

2. Spending too much on impulse purchases

The average American spends around $5,400 per year on impulse purchases, a survey from deal-sharing platform Slickdeals found. That amounts to around $324,000 over a lifetime.

Impulse purchases are tempting because alone, they seem insignificant. After all, how much effect could a $2 candy bar or $20 shirt have in the long run financially? But when you add up all those purchases, they can have a serious impact on your ability to save.

Say you're trying to save for retirement, and instead of spending $5,400 per year on impulse purchases, you invest that money in your retirement fund earning a 7% annual rate of return. After 30 years, your savings will amount to around $510,000.

Keeping your impulse spending in check can be more challenging than it sounds. The majority of people buy on impulse because they think they're getting a good deal, Slickdeals found. But if you're not going to make good use of the product, it's still a waste of money -- no matter how great the deal was. Before you buy anything, ask yourself whether this purchase is necessary or in your budget. It's OK to splurge every so often to treat yourself, but make sure those purchases are planned and accounted for so you don't blow your budget with impulse spending.

3. Putting off saving until you have more to save

It's tempting to tell yourself that the reason you can't save now is because you can't afford it, and you'll start saving more once you finally earn that raise or begin a new job with a higher salary. But wait too long to start saving, and it will be exponentially more difficult to catch up.

This is especially true for larger, long-term goals like saving for retirement. You may need upward of $1 million saved to retire comfortably, and it takes several decades to save anywhere near that amount. Say, for instance, you want to retire at age 65 with $1 million in your retirement fund. If you were to start saving at age 25, you'd need to stash away around $425 per month to reach that goal, assuming you're earning a 7% annual rate of return on your investments. But if you wait until age 35 to start saving, you'd have to save roughly $900 per month, all other factors remaining the same.

Even if you don't have much to save now, it's better to set aside what you can rather than putting it off for another day. Wait too long, and you may end up like the half of U.S. adults age 55 and older who don't have a penny saved for retirement. That day will be here before you know it, and the earlier you start saving, the easier it will be to reach your goals.

No matter what financial goal you're saving for, stashing money away isn't easy. But you may unknowingly be making it more challenging than it needs to be by falling victim to these dangerous financial habits. Once you're aware of how they affect your bank account, though, saving may not be as difficult as it seems.