Whether you're gearing to retire in a handful of years or a few decades down the line, the more thoroughly you prepare, the more likely you are to be able to enjoy your senior years to the fullest. But part of preparing well for retirement means steering clear of dangerous myths that could lead you astray. Here are four you cannot afford to buy into.

1. Social Security will cover all of your expenses

Many people assume that once they retire, they'll be just fine if their only income source is Social Security. Little do people in that boat realize that Social Security will generally only replace about 40% of pre-retirement wages. And that assumes two things -- that you're an average earner, and that benefits aren't cut in the future.

Image source: Getty Images.

Most retirees need about 70% to 80% of their former income to live comfortably. But some people need more. It all depends on the lifestyle you're aiming for, the state of your health, and other factors.

Either way, do not assume that Social Security will cut it for you in retirement. Save as best as you can in an IRA or 401(k) for the tax benefits. And if you're close to retirement and missed out on an opportunity to build your nest egg, consider continuing to work in some capacity once your main career comes to an end.

2. Social Security is going broke

You get choices when it comes to claiming Social Security. Your benefits are yours to collect without a reduction once you reach full retirement age, which is 67 for people born in 1960 or later. However, you're allowed to claim Social Security starting at age 62.

Each month you file ahead of full retirement age reduces your benefits to some degree. Filing at 62 with a full retirement age of 67 results in a 30% reduction.

You may be planning to file for Social Security as early as possible because you think the program is going broke, so you might as well get your money before it runs out. But that's not what's happening.

As mentioned earlier, Social Security is in danger of having to cut benefits in the future. But it's not in danger of stopping benefits completely.

Social Security is primarily funded by payroll taxes, which helps ensure that the program will continue to have money coming in. It may not be enough money to pay scheduled benefits in full, but it should be enough to pay something.

As such, you may not want to plan on claiming Social Security as early as you're allowed to. If you reduce your benefits by filing early and then there's a broad reduction, you could end up with very little income from the program.

3. Your expenses will decrease substantially in retirement

Many people assume that once they retire, they'll start spending a lot less. In reality, the only costs you might shed are those that relate directly to your job.

You obviously won't have to pay to commute if you're no longer working. But retiring won't change your mortgage payment (if you still have one), property tax bill, or grocery costs. It also won't eliminate the need to pay for heat, water, and electricity. If anything, those costs might rise, since you may be home more often.

Plus, some of your costs might increase in retirement. You may find yourself spending more on healthcare or leisure activities. Save accordingly so you don't end up with an income shortfall on your hands.

4. Taxes aren't something retirees have to worry about

You might assume that the IRS will let you off the hook as far as taxes go once you retire. That couldn't be further from the truth.

There are many retirement income sources that are subject to taxes. These include:

• Traditional IRA or 401(k) withdrawals
• Social Security benefits
• Dividends or interest payments on investments held outside of retirement accounts

It's important to plan for taxes in retirement, and to work with a professional to try to minimize them. One strategy could be to do a Roth conversion ahead of retirement if your savings are currently in a traditional retirement account.

You can also choose your investments strategically. Municipal bonds, for example, can be a reliable source of income, and the interest they pay is exempt from federal taxes.

The last thing you want is for misinformation to wreck your retirement. Make a point to get to the bottom of these big myths so they don't end up ruining your senior years.