"I don't have to work, I need to work. But I have a good work ethic. David has an incredible work ethic. I want my kids to have a good work ethic. I believe you can achieve anything if you work hard enough to get it," she said.
The 38-year-old former Spice Girl also said juggling her fashion business with motherhood had left her exhausted.
"I'm not going to lie about it, I'm tired. I'm really tired but I'm also very happy with my life. I'm basically just like any woman who's working and has lots of children - it's tough.
"I'm not getting much sleep at all. Harper's not sleeping that great, and I've been taking Skype business calls throughout the night too because of the collections," she added.