productivity - Ways to manage something like a 'work-life balance'?

According to a recent international study on work-life balance within academia

"a majority of researchers and scientists had conflicts between their work schedules and personal lives at least two to three times a week."

Nevertheless,

"about 60 percent of scientists were happy with their work-life balance. The rates for women were lower, at 52 percent."

I wonder what differentiates these 60 percent 'happy people' from the remaining 40 percent. What do you think are good strategies for a healthy work-life balance? How do you balance your academic work/life with your personal life?