For many Americans, retirement means living the rest of your life on fixed income. But, if you did the proper planning, that fixed income might even sustain the lifestyle you lived during your working life.

The last thing you need or want is something that can create havoc on your income. And that's why you must be prepared for those an unexpected expense -- things that may be a shock to your retirement lifestyle.

Fixing that car or replacing that furnace was tough enough when you were working. But when you are on a fixed income, it could mean disaster.

That's why financial planners generally recommend that retirees have an emergency fund.

"Sometimes you have people ignoring the possibility of something bad happening in financial situation," says Bryan Hoover at Fragasso Financial Advisors in Pittsburgh.

In any event, there are certain shocks - not all of them financial - that can mean trouble for retirees. Not all of them are financial. Some are purely emotional, but just as devastating.

Here are a few financial planners say are not uncommon.

1. Loss of a job. One of the most devastating of all is losing your job. This can be especially troublesome if you lose that job before you had planned and are forced into an earlier than expected retirement. But it also means that money you expected to earn - and save - will no longer be available. On top of that, you may have to start drawing from your retirement savings earlier than you expected.

"Someone loses a job or stops working - that's a big deal," says Hoover. "That led to $2.5 trillion in lost retirement savings. People stop saving because they are hitting a wall." 

2. Unplanned medical expenses. "Health care costs definitely (are a shock)," says Nina O'Neal, partner at Archer Investment management in Raleigh, N.C. "Second is not factoring in increasing health care costs in longevity." 

She says some people retiree too early and have to go back to work to create income to cover major medical costs, especially since people are living longer.

"Before 65 is very expensive for a couple," says O'Neal. "It can be a significant line item." 

Also, many people underestimate Medicare costs. "Medicare is a great benefit at 65," says O'Neal. "However, it still has costs to each couple. That cost will be your co-pay, your deductible, co-insurance or supplemental. That can run a person somewhere $6,000 a year. They also have to pay for Medicare. It is not free health care. There are still costs. "

3. Health insurance. Health insurance can be a big shock for people who retire at 60 or even 62. Many forget that they have to pay for health insurance until they turn 65 and qualify for Medicare. That can be substantial for someone who has had their company pick up half the cost for years. Some government workers and some large companies will keep you on your insurance roles during this time, but most companies today will not."Inflation is definitely an issue, especially people who retired 20, 30 or 40 years ago, and still on that same income," says O'Neal. "The cost of living has increased. It costs a lot more to do things like buy a car."

4. Seven Days of Saturday. "There is in our industry the rumor that you only need 80% of your current income in retirement," says O'Neal. "I always ask what goes away? I've never seen anybody spend less in retirement. Most people are living the same now that they have seven days of Saturday." 

"You enjoy life," she adds. "You take more trips. You visit family. You are not typically going to sit home for seven days. What will you spend money on so you can enjoy retirement. But don't make the assumption that you will decrease amount of money you spend." 

5. Unexpected loss of a spouse. "I've seen that as the most devastating," O'Neal says. "You have a mental picture of your Golden Years, and they usually include someone that's been there your whole life. We've worked through that with widows and widowers. But the whole financial picture changes immediately. Some women have not had experience with finances. If it's a spouse that has not been involved in finance, that's a huge shock. They didn't plan to take the responsibly."

Hoover says that even though many of the shocks are unexpected, there are things you can do to better prepare.

"You feel helpless when you consider those things are possible," he says. "There are lots of things you can do to put yourself in position to weather those storms. Start saving at an early age. Spend widely, not a lot of focus on discretionary items. It's about habit forming. If you prioritize correctly, even a loss of income won't interfere with your ability to save."

"And avoid debt," he adds. "Lots of folks are either paying mortgage or paying student loan. The more flexibility to have to avoid fixed payment, the more you can save."