10/13/2008 at 08:00 AM EDT
What prompted Jennifer Love Hewitt
to get serious about her workout regime?
No, it was not
those infamous bikini pictures
– or the nasty blog comments that followed.
"I'm getting ready to turn 30 and get married and all those things," she tells PEOPLE, echoing the diet motivations of countless women. "This year was my year to try to glow from within and feel better."
The actress looked slim and stunning Saturday night as she hit L.A.'s Runway For Life event benefiting the St. Jude Children's Research Hospital, presented by Disney’s “Tinkerbell”
DVD, on the arm of fiancé Ross McCall
. Her exercise plan?
"I work out about four or five days a week," she said, strutting her stuff in a slinky purple dress by Carmen Marc Valvo. "I love to run – that's good."
In addition to cardio, the former Party of Five
star also mixes in strength moves.
"I'm perfecting my pushup right now," she said. "And the plank pose is very inspiring – where you're up on your elbows and your legs are out, and it's just your stomach holding your body up. Very cool."
The actress says she wants to have children with the Scottish actor "someday." In the meantime, she's enjoying the opportunity to focus on her health.
"The better you are in your mind, body and spirit, the better everything goes for you in your life," she added.
2007: Jennifer fires back and defends her bikini body