You want to retire comfortably, and that can be a tough task to complete. The statistics prove it -- according to a recent study, median retirement savings among workers aged 60 or older is a meager $172,000. That amount supports annual retirement withdrawals of less than $7,000.

To get different results in your 401(k), you need to avoid the mistakes others have made. So welcome to 401(k) bootcamp, recruit. If you want to survive out there as a retiree, without a paycheck, you will not commit these eight 401(k)-killing blunders.

1. Not contributing

If you have a 401(k), use it. Saving with pre-tax money is more efficient than saving with after-tax money. You'll also benefit from tax-deferred earnings growth, which helps you build wealth momentum faster.

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2. Not choosing investments

Your contributions are dying out there as uninvested cash or money market deposits. Log into your 401(k) portal and set your investment selections.

Or, if your plan assigned you a default fund, research it. Switch to something else if that fund doesn't suit your timeline or risk tolerance.

3. Not taking your full employer match

Your employer match is free money, there for the taking. You may have to stretch your contributions to get the full match -- find a way to make it work. Because those added contributions, combined with your match, can double or triple your savings over time.

4. Withdrawing money early

A 401(k) loan or early hardship withdrawal lowers your balance and your earnings potential. Bouncing back from that can be tougher than a 30-foot rope climb in full dress on a hot day. You can increase your contributions, but you'll be working against the compound earnings you would have made on the borrowed or withdrawn funds.

5. Picking investments based on recent performance

Broader trends in the stock market heavily influence fund performance. In down markets, your equity fund options will show negative results. In inflationary periods, your bond fund options may also show negative results.

Right now, we're experiencing a down market with inflation. A short-sighted analysis could push you into cash since your other options don't look great. If that's where your head's at, scroll back up and read the second mistake again.

Look instead at how funds perform relative to their benchmark index across 10 years or more.

6. Not increasing your contribution rate annually

It's not enough to collect your full match and then hold your contribute rate steady. To maximize your wealth potential, increase your contribution rate at least once a year. Stay on that habit until you hit the 401(k) contribution limit.

7. Investing too conservatively

If you're younger than 45, it's a mistake to invest too conservatively. You'll miss out on growth opportunities -- at a time when you can afford to take risks.

You can afford the risk because you don't need the money right away. Any down cycles (like the one we're in now) should resolve themselves before you start taking retirement distributions.

8. Investing too aggressively

If you're older than 50, an aggressive strategy in your retirement account can backfire. Investing aggressively increases risk and volatility. You could see wild swings in your account balance as you near retirement, which you definitely do not want.

As you age, protect your wealth and minimize volatility by getting more defensive in your approach.

Completing your mission

You have a 401(k), which means you have the tools you need to retire comfortably: a job and a tax-advantaged account. Now, march forth and use them. Contribute, invest, and let your wealth grow -- for decades, if possible. That's how you get from 401(k) boot camp to wealth-mission accomplished.