For Broadway vet Idina Menzel, the best day of her life was welcoming son Walker Nathaniel Diggs into the world.

On Sept. 2, 2009, Walker took his first breaths after a serene, natural birth. "I wasn't all drugged up," shares the Frozen star with Closer.

"It was amazing because they say that babies don't really look at you, but I feel like the two of us stared into each other's eyes. We weren't doped up on some epidural, and I could say, 'Hi. Welcome to the world.'"

It was love at first sight for mama and baby (whose father is Taye Diggs, Idina's now-estranged husband), and the 43-year-old confides that life has never been better.

idina menzel

Idina with now-estranged husband Taye Diggs in 2009

"It's changed everything," Idina gushes. "Being a mom's made me tired, so I've lowered expectations of myself and am more relaxed."

She adds, "It's made me not sweat the small stuff and be in the moment. I end up enjoying myself more…I like who I am as a mother."

And adorable Walker, now 4, has become her biggest fan. At a recent party, he told friends, "'Oh, my mommy sings songs from Frozen.' And they said, 'So do our mommies!'"