Woman putting coin into piggybank  © Brigitte Sporrer, Getty Images

You don't want your retirement savings to be a case of "shoulda, woulda, coulda."

But for many of us, the biggest problem is that we take a little "savings vacation," stop socking money away, then never get back on track.

Let's say, for whatever reason -- from an unexpected medical bill to paying for college tuition -- you took out a loan from your 401k or cashed out your retirement savings when you changed jobs. And you have yet to replace the money you took out.

If that describes you, you're hardly alone. One in every five participants who withdrew money from a 401k plan in 2011 hadn't paid themselves back by the end of the year, according to the Employee Benefit Research Institute (EBRI). New research from financial technology firm HelloWallet shows that more than one in every four participants are using their retirement money to pay for nonretirement needs.

Of course, sometimes, life interrupts your best savings plans. We get it. But take heart -- saving for retirement is a lot like riding a bike: If you fall off, you can always get back on. Here are three key steps to get you saving again:

No. 1: Rebuild your emergency fund

First things first: You need an emergency fund, so you won't be tempted to stop saving for retirement or use money earmarked for it when a crisis hits. "You still need to make sure you have some sort of emergency savings so you don't crawl back into the same hole," says Judy McNary, a financial planner in Broomfield, Colo.

An emergency fund, which should be at least six months of net income set aside in a separate account, is also the smartest place to pull money from in a financial crisis, says Joel Bengds at HSC Wealth Advisors in Forest, VA. "Folks always feel they can make up the difference in the years to come," he says, but most never replace money in a retirement account.

Besides, while there are only certain times you should withdraw from an emergency fund, it's far more detrimental to make an early withdrawal from a retirement account. In most situations, you'll incur a 10 percent penalty fee and pay taxes on your withdrawal, eating into the money you took out. That means you'll have to save even more to replenish what you "borrowed."

In addition to keeping your hands off your retirement savings, an emergency fund delivers another benefit: You'll likely think twice about spending that money, for the simple reason that it took you time to build it up. "People are much more intentional and scrutinizing when pulling money out of an emergency fund," says Bengds.

No. 2: Find your wiggle room

Most people who don't save think they have no "room" to do so, but never look to see where they might free up the extra money. "It all starts with a simple budget," says Bengds.

It's easy to make excuses -- at any age or income level -- for why you just can't put more toward retirement: Older workers grow accustomed to luxuries, he says, "while younger clients want to have all the luxuries now—the house, the furniture, the car -- that their parents worked hard to enjoy."

Finding the means to plump up your retirement account usually involves a three-fold effort: First, controlling your "urge to splurge," tracking your expenses so you know where your money is going and "paying yourself first" by putting set amounts away in both an emergency fund and a retirement account.

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