If the thought of retirement is stressful, it s no wonder. With traditional pension plans on the wane, and life expectancies on the rise, the onus of saving enough for retirement is entirely on American workers, and they have to figure on supporting themselves for some 30 years.

While polls show that many folks approaching retirement age plan on working either part- or full-time to keep themselves occupied, most people would like to have the option to fully retire if they want to.

When you can retire and whether you should consider a part-time job in retirement for financial reasons depends on these two important questions:

How Much Do You Need?

Regardless of your goal traveling the globe or spending time with your grandkids your first task should be to get a handle on how much your ideal retirement will cost. Many financial planners use ballpark figures, such as 80% to 100% of your preretirement income, adjusted for inflation. That would be quite an ostrich-size nest egg.

But before you start bulk-ordering mac 'n' cheese, know that many experts say retirees can live quite comfortably on far less. In fact, you're probably already doing so. Right now, for example, a significant slice of your paycheck might be going straight into retirement savings, reducing your take-home pay by perhaps 10%. And on the expense side, you might be on the cusp of paying off your mortgage, or planning to downsize your home or move to a lower-cost area all endeavors that would cut your monthly nut.

For what it's worth, some retirees also swear that managing expenses is far easier after retirement than it was beforehand. In many cases, for example, kids have flown the coop and the mortgage has been paid off.

Where's the Money Coming From?

Chances are, you'll fund your retirement through various income streams and your investment portfolio, including your 401(k) and IRA. How much you need to lean on that portfolio depends on how much other cash is coming in each month. So add it up.

Defined-Benefit Pension Plans. These traditional pension programs offer regular payments throughout retirement. If you qualify for one and you've worked at your company for many years chances are this will represent a big chunk of your retirement income. Be sure to ask how much your benefit would increase if you were to work an extra year or two.

Social Security. Looming shortfalls in coming decades have prompted calls for benefit reductions, means testing or both. For now, however, the system remains solvent, and there's nothing happening on the political stump to indicate that any change is imminent for Americans who are nearing or in retirement. You can begin receiving full retirement benefits between age 66 and 67, depending on what year you were born. For each year beyond that you wait to begin collecting Social Security, your benefit increases by up to 8% until age 70. If, however, you tap Social Security as soon as you're eligible, at age 62, your benefit will be reduced by about 25%. You can request a Social Security estimate via the Social Security Administration's Web site.

Part-Time Work. Surveys by the AARP and other organizations show that the majority of pre-retirees plan to work during retirement. Some will take on consulting work, others will begin new, less ambitious careers, and still others will turn to the most vibrant part of our economy: small businesses. But you should be realistic as to how much you expect to earn. The pay scale in corporate America can be much greater than at a small business.