08/11/2009 AT 03:50 PM EDT
New mothers are often advised to never wake a sleeping baby, and Angela Kinsey learned the hard way why.
star told PEOPLE's Celebrity Baby Blog she tempted fate one day with her 15-month-old daughter
Isabel Ruby – with disastrous results.
"I was like, 'You know what? She's taking a late afternoon nap, she's not going to fall asleep 'til late, I'm going to pick her up and rock her to see if she'll wake up,' " the actress recalls. "Mistake! My mom was right."
Isabel's tears that day were hopefully short-lived, but Kinsey, 38, admits she often cries "tears of happiness" when gazing at her first child.
"[Costar] Steve [Carrell] told me when I was pregnant 'Every cliché you hear, you will say or experience.' He was absolutely right. ... I can't believe she's mine. I can't believe I've been so privileged to have this experience."
Kinsey counts the Boppy
and Cheerios among her mommy must-haves; With regard to the latter she notes, "If I don't have them in a Ziploc in my purse then I'm screwed!"
From the sound of things, Isabel is more impressed by a certain fuzzy red friend familiar to many moms, however. "She said 'Elmo' this morning for the very first time," Kinsey proudly reports.
"She pointed to the TV and said 'Elmo' and I was like 'You are a genius! You will cure cancer!'"
Isabel is Kinsey's daughter with estranged husband
The new season of The Office
premieres Sept. 17 at 9 p.m. on NBC.
Reporting by SCOTT HUVER