Photo: flickr user Dan Moyle

Even if you've saved responsibly your entire life, that doesn't mean you're guaranteed an enjoyable retirement. There are still some things that could become financial drains on your nest egg that you need to be aware of. For example, you still need to budget properly and account for certain potential expenses. With this in mind, we asked three of our retirement experts to tell us about what they feel are the biggest threats to your financial security in retirement, and here is what they had to say.

Matt Frankel: One way you could easily run out of money in retirement is by underestimating your healthcare expenses. According to one recent study, a 65-year-old couple retiring now can expect total out-of-pocket medical expenses of $394,954 throughout their retirement, including things like co-pays, dental care, vision care, and other health-related expenses.

This isn't expected to get any better over the coming years. The same study predicts that a 55-year-old couple planning to retire in 10 years at age 65 will face retirement health care costs of $463,849.

Wages and Social Security have not grown (and are not projected to grow) nearly as rapidly as healthcare expenses, so it's very important to account for the potential healthcare costs when planning for retirement. There are a few strategies you can use to do that.

For example, if you have a health savings account, or HSA, you can leave money in there to grow and compound as long as you'd like. Or, you can increase your IRA contributions. A $150 monthly increase to your IRA contributions could mean an additional $300,000 in 30 years, assuming the S&P 500's historical rate of return.

Finally, the least costly strategy is to take optimal care of your health now. Although nothing is guaranteed as far as health is concerned, studies have shown that people in good health spend about 20% less on healthcare per year than people in poor health.

The point is that there are steps you can take now to lower your post-retirement healthcare expenses and to plan for them financially, and doing so can prevent you from running out of money in retirement.

Selena Maranjian: The money you've socked away for retirement has to last you as long as you (and perhaps your spouse) live. Some expenses in retirement will be out of your control: You can't, for example, be guaranteed a low inflation rate, and no one knows what their ultimate total healthcare costs will be in retirement. Many expenses are under your control, though -- and an important thing to keep in check is your generosity.

Many retirees find themselves suddenly with a big nest egg they're drawing from, and a paid-off home, and a little more time on their hands to think about their loved ones, now that they're not working. If your kids or other loved ones are struggling financially, it can be tempting to jump in and help. It might feel like you have a lot of money, when they don't. But remember -- you might need all that money that you have.

I don't mean to suggest that you should leave loved ones to flounder, but do think hard about gifts you give and about whether any loans are likely to be paid back. If a child is out of work and needs money for rent, you might invite him back home to live instead of agreeing to write an undetermined number of rent checks. (Of course, having a long-term houseguest might not be a welcome development, either.)

According to a 2012 MetLife survey, some 62% of grandparents financially assisted their grandchildren either directly or through their parents in the past five years, with gifts that averaged $8,289. A third of these folks indicated that their generosity is negatively affecting their own finances, threatening their retirement. It's good to be generous in retirement, but aim to do so on a small scale, if possible. Big gifts can lead to big trouble.

Jason Hall: One simple way to run out of money in retirement is fail to adjust to your new income, and develop spending habits that will sustain your nest egg.

It may sound simple to just make a budget and stick to it, but once you're no longer earning a paycheck, and your income becomes fixed, the things you spend on that you left out of the budget can really add up. Two big areas are the ones that Matt and Selena describe in their contributions to this article.

What can you do about it? Three things:

  • Create a margin of safety in your budget, by adding an amount for unexpected things like car and home repairs.
  • Be disciplined to that budget, especially when you first retire.
  • Increase your retirement savings today to increase your margin of safety when you retire.

It may sound like an oversimplification, but the more money you save, the less likely you are to run out. Just as importantly, though, is creating good spending habits early in your retirement (actually this should start before you retire). It may seem like you've got plenty when you look at the balance in your retirement account, but longer lives, higher healthcare costs, and lower rates of return for fixed-income assets like bonds make it more important than ever that you learn to stretch every dollar farther.

Don't get me wrong: Retirement shouldn't mean you have to live like a pauper. But if you want to avoid being forced to live like one in your later years, then it's best to develop healthy spending habits at the beginning of your retirement.