Alongside her admission, Rebecca shared a powerful quote about the realities of becoming an empty nester.
"When mothers talk about the depression of the empty nest, they're not mourning the passing of all those wet towels on the floor, or the music that numbs your teeth, or even the bottle of capless shampoo dribbling down the shower drain," it read.
"They're upset because they've gone from supervisor of a child's life to a spectator. It's like being the Vice President of the United States."
The good-humoured actress followed that quote up with a cheeky meme featuring a list of "rules for dating my son", clearly meant as a tongue-in-cheek reference as Zac starts life at uni.
From "I am everywhere" to "I do better research than the FBI", the joking rules prove that even at a bittersweet moment like this, Rebecca still has a sense of humour about the situation.
Now that Zac is off studying in Wellington, Rebecca and Richard will be sending their love from afar, as they live in Dunedin on New Zealand's South Island.
Though we're sure Zac will be home for the holidays and plenty of family visits, it's clear that his parents are already missing him – and it's only been a day!
Over the weekend Rebecca shared a tribute to Zac's relationship with his father, proving that she won't be the only one missing the teen while he's away.
Posting a series of photos of Zac and Richard through the years, the 57-year-old recalled how the father-son bond developed through the last 17 years.
"Whether holding him in the palm of his hand, resting on his chest, sitting high on his shoulders, to walking side by side, and even now sleeping on each other's shoulders - Zac knows his father will always be here," she wrote.
"We are a lucky family indeed."
Though Rebecca and Richard will undoubtedly miss Zac while he's away, it's clear that they couldn't be happier for him as he starts the next chapter of his life.
This story originally appeared on our sister site, Now To Love.
