These Rookie Investing Mistakes Can Kill Your Portfolio

"Investing should be more like watching paint dry or watching grass grow. If you want excitement, take $800 and go to Las Vegas."--Paul Samuelson, Nobel Prize-winning economist

They say investing is a marathon, but not everyone is naturally equipped for endurance. Building a strong financial portfolio requires patience, knowledge, and forethought, and it can be difficult to spot poor decisions until the damage is done. Above all else, avoid the money busters below -- your net worth depends on it.

1. Not saving enough for retirement

Sure, it's not exciting, but the main objective of investing is financial security, and you owe it to yourself to think about your golden years before funneling cash elsewhere. According to a 2017 Merrill Lynch survey, the average price tag for a 30-year retirement starting now is $738,400. While this may seem like a lot, it works out to just $24,613 per year.

If you think you'll need more than "average" to enjoy retired living, you can't afford to waste time. Begin maxing out your 401(k) contributions as soon as possible: Not only will you rapidly grow your savings and thus the interest they earn, but you'll receive the full amount your employer matches (if any), which will supercharge your portfolio's growth.

For example, let's suppose your salary is $80,000 and you contribute the annual maximum of $18,000 to your 401(k). Assuming a 7% annual return, you'd save nearly $1.8 million in 30 years. Now let's suppose your employer matches up to 6% of your annual contributions. Without saving another dime, your account would skyrocket to $2.2 million.

2. Chasing "the next big thing"

Americans are an impatient lot. A Fifth Third Bank survey found that more than half of us hang up the phone if we've been on hold for more than a minute, and 96% would rather burn our mouths than wait for food and drink to cool down (yes, really). We love quick results, and while you may be looking to invest in the next Apple (NASDAQ: AAPL) or Amazon (NASDAQ: AMZN), the truth is that many companies, including these tech giants, took years to grow their businesses (and share prices).

While it's important to educate yourself and stay on top of emerging companies, investing based on media hype and the hope of short-term profits could leave you financially and emotionally wrecked. Before investing in the latest trend, research every prospective company's earnings, history, and outlook, and consider how your decision will affect your portfolio's overall diversification.

3. Ignoring fees

You might dismiss investment fees as the cost of doing business. Worse yet, you may not realize they exist at all -- and you wouldn't be alone: A 2011 AARP study revealed that 71% of participants didn't think they paid any 401(k) fees.

The reality is that every 401(k) plan charges fees called expense ratios, which are assessed annually as a percent of your invested assets. Employer-sponsored plans tend to have lower expense ratios than equity mutual funds, and it's important to know the national averages of both to determine how your investments fees compare. Excessive fees can cost you tens or hundreds of thousands of dollars over the course of your lifetime.

When it comes individual stocks, the costs of active trading can add up quickly. Not only will you pay a trading fee, but brokerage firms can charge you for operating costs like per-trade commissions, account transfer fees, annual fees, inactivity and minimum balance fees, and more. Without the right attention, these costs can eat away at your earnings. Read the fine print to ensure that you aren't sacrificing too much.

4. Letting your emotions drive

For many people, investing is an emotionally polarizing experience, and there are a lot of external forces at work: market shifts, the political climate, individual company performance, etc. Whether you're itching to cash in after a company's latest earnings report or you're fearful after a market dip, leading with your feelings is rarely the right choice.

The best way to sidestep emotional decisions is to create an investment plan and stick to it. While you shouldn't hold every asset to the same rules, you should have an end-game in mind to help you avoid feeling swayed by underperformance, the temptation to withdraw gains, and overtrading. The sum of these emotional responses is usually a missed chance to benefit from compounding interest and greater returns.

There will always be an attractive buy on the table, but that doesn't mean you should abandon your strategy and risk your long-term wealth. Stay strong in your commitments and resist the urge to wander.

The $16,122 Social Security bonus most retirees completely overlook If you're like most Americans, you're a few years (or more) behind on your retirement savings. But a handful of little-known "Social Security secrets" could help ensure a boost in your retirement income. For example: one easy trick could pay you as much as $16,122 more... each year! Once you learn how to maximize your Social Security benefits, we think you could retire confidently with the peace of mind we're all after. Simply click here to discover how to learn more about these strategies.

Sarah Szczypinski has no position in any stocks mentioned. The Motley Fool owns shares of and recommends Amazon and Apple. The Motley Fool has a disclosure policy.