The Secrets to Handling 'Mommy Guilt'

— -- Countless moms confess in online message boards and blogs to feeling a nagging sense of inadequacy when it comes to balancing work and motherhood. They call it, "mommy guilt."

“I do feel that guilt, especially when I’m trying to get away from my children to get some work done, where I feel like, ‘Gosh, I wish I could just focus on my kids,’” Allison O’Kelly, who has three sons and is also the full-time boss of her staffing company Mom Corps, told ABC News’ “Nightline.”

More than 70 percent of American women with children under age 17 are working moms, according to the U.S. Department of Labor. But now, a growing number of professional women are choosing to focus on their kids instead. The share of stay-at-home mothers rose 29 percent in 2012, up from a modern era low of 23 percent in 1999, according to a Pew Research study. And this May, Harvard Business school released a survey that showed 37 percent of millennial women planned to leave the work force for family, compared with 28 percent of Gen X women and 17 percent of baby boomers.

But Laura Vanderkam, the author of “I Know How She Does It,” says women with “big jobs have much more balanced lives than people often think they do.”

“There’s a story out there that women just can’t have it all,” Vanderkam told “Nightline.” “I found that that was not the case. I wanted to show with this book that there are many women who are juggling work and life just fine, and that it can be done.”

A working mom to four kids herself, Vanderkam said she found the secret to work-life balance by analyzing hour-by-hour time logs from the lives of over 100 successful, high-powered working moms.

“Looking at how you spend the time is often the best antidote for guilt. When we see where our time actually goes, we can make better choices,” Vanderkam said.

To learn how to make best use of that time, “Nightline” recently enlisted O’Kelly, of Philadelphia, to keep her own detailed diary hour-by-hour of her time during a day in her life for Vanderkam to review.

While her two older sons, 12-year-old Nolan and 10-year-old Ethan, went to camp that day, a babysitter watched over her 4-year-old son Declan. O’Kelly then headed to her home office where she began work. However, throughout the day, Declan would interrupt O’Kelly in her office seeking his mom’s attention. In the evening, O’Kelly sat with her sons in front of the TV while returning work emails.

“It’s challenging. You feel bad. You would love to have them come and watch TV, but I work, so you have to get your job done so you don’t really have a choice, but it is hard,” O’Kelly said.

Since O’Kelly had no line dividing work and family time, Vanderkam suggested she set clear boundaries by employing what she called a “split shift.”

“End work at a reasonable time. Hang out with the family. Go back to work after the kids go to bed. By enforcing the 8:30 to 9 block for work you can get done what you need to get done,” said Vanderkam.

By doing so, Vanderkam said O’Kelly can keep her son out of her office with the promise of her full, undivided attention at the end of the work day.

Vanderkam also suggested that moms like O’Kelly try to be creative when scheduling quality time with their children. For example, instead of doing chores in the morning, Vanderkam said that time can be put to better use.