The mother-of-three shoots the cop drama in Los Angeles, while her husband Jason Sehorn and their little girls are on the other side of the country in Charlotte, North Carolina.
Harmon admits she is struggling to cope with being apart from her kids, Finley, seven, Avery, six, and two-year-old Emery.
In an emotional interview with Good Housekeeping magazine, she explains, "I'm a mess. I've lost 10 pounds since I got here. This is the hardest time in my life, for sure.
"When I feel like I'm not doing what I am supposed to as a mother, I will torture myself. I don't know how to deal with it. I find some consolation in the fact that all mommies feel it. If there was a way to cure mommy guilt, I would bottle it and be a bazillionaire.
"It breaks my heart that I don't see my daughters every day, don't get to hug them and brush their hair."
But Harmon won't consider relocating her family to California, insisting, "There’s a church on every corner (in North Carolina) as opposed to just a Starbucks. The people are just a little nicer... more real."