While the biggest factor in deciding when to retire is whether you still need or want to work, there are many other variables to consider to ensure a comfortable and secure life after work. "There is an upward trend in Americans working beyond age 60," says Gary Burtless, Ph.D, research associate at the Center for Retirement Research at Boston College. "And we've seen an increasing number of people staying in the workforce until age 72." Burtless says that the incentives within the Social Security system and employer-matched 401(k) plan contributions can make working later in life more financially attractive. In addition, American's confidence in their ability to retire comfortably is at an all time-low. According to the 2012 Retirement Confidence Survey by the Employee Benefit Research Institute (ERBI), 60 percent of workers report having less than $25,000 in savings or retirement assets. Beyond the financial retirement considerations, Elizabeth F. Fideler, Ed.D., researcher and author of "Women Still at Work: Professionals Over Sixty and On the Job" and a forthcoming book on aging men in the workforce, found that a main reason would-be retirees choose to keep working beyond age 60 is that they enjoy the work and the feeling they are contributing and making a difference. How can you know whether you're ready for retirement? Asking yourself these six questions may help. Any "no" answers may mean it's worth waiting a little longer to retire.