Source: Flickr user Ed Yourdon.

Early retirement is a goal of many Americans, and it can be achievable with the right savings discipline and investment strategy. However, if early retirement is on your wish list, make sure you know what you're getting into. There are some expenses and issues that come with leaving the workforce early that need to be incorporated into your planning.

You may have to provide your own health insurance
This isn't quite as big of an issue as it used to be. After all, the Affordable Care Act did make health insurance a little more, well, affordable -- especially for older adults. However, if you plan to retire early, this is still something you need to take into consideration.

If you retire early in certain jobs (particularly in the public sector), you could continue to receive health benefits after leaving work. If this applies to you, consider yourself fortunate. However, many early retirees will need to provide their own health insurance to bridge the gap between retirement and when Medicare kicks in at age 65.

According to the latest data, a mid-level health insurance plan costs an average of $470 monthly for a 55-year-old. So if you want to retire early, factor this expense into your planning.

You'll need access to your nest egg, or at least some of it
So long as you wait to retire until you're 59-and-a-half years old, this shouldn't really be an issue. However, if you decide to leave the workforce at say, 55 years old, make sure you'll have access to your retirement savings.

For example, if you've been saving your money in a traditional IRA, you may not be able to withdraw your contributions early without incurring a 10% early-withdrawal penalty from the IRS. On the other hand, with a Roth IRA, you can withdraw your original contributions at any time without penalty -- but not any investment gains.

Your 401(k) plan may have similar rules to a traditional IRA. However, if you separate from service after age 55, there is a provision that allows penalty-free withdrawals. There are some other situations where you may be able to withdraw money from your retirement savings early. This list from the IRS provides a good overview.

However, even if you might be able to get away with withdrawing your retirement savings early, it may not be a good idea. After all, one of the best investment tools at your disposal is the tax-free compounding you get with an IRA or 401(k).

If you're planning to retire early, it might be a good idea to have some money outside of your retirement accounts, whether you use standard brokerage accounts, CDs, or any other non-age-restricted form of savings. If you retire at 54, it may be a good idea to budget for five years or so of living expenses outside of your retirement accounts.

If all of your money is in IRAs and 401(k)s, at the very least, you need to have a plan for accessing your money without incurring a penalty. It may be a good idea to make sure you can withdraw from your 401(k) through one of the early-withdrawal exceptions until you reach full retirement age. If this applies to you, ask a professional financial planner what your options are.

Social Security will still be years away
This may not be a big issue if you have enough money saved to retire early. But when you figure out how you'll come up with your living expenses, take into account that the absolute earliest you'll be able to collect Social Security is at 62 years old -- and it's beneficial to wait even longer if possible.

Your benefit goes up significantly for every year you wait until you reach age 70. For example, if your Social Security benefit at your full retirement age of 67 (if you were born after 1960) is expected to be $1,000 per month, by waiting until 70, you can increase that amount to $1,240. On the other hand, if you start collecting at 62, your monthly benefit will be reduced to $700.

Know what you're getting into
I'm not saying that early retirement isn't a good goal. On the contrary, early retirement can be an excellent motivator for responsible saving and investing, and it can ultimately lead to more free time while you're still young enough to make the most of it.

Maybe all of these things don't apply to you. For example, many public-sector jobs continue to provide health benefits for retirees after a certain length of employment, regardless of age.

However, the takeaway here is that simply saving and investing like you would for a normal retirement age isn't good enough. You need to plan for all of the additional challenges that come along with retiring early. If you do, early retirement can be a reality instead of just a wish.