You may know her as Clarissa or Sabrina, but if you ask actress Melissa Joan Hart, her most important role is Mom. When she’s busy traveling for work (the funny lady, 43, is currently starring in Christmas Reservations) and keeping up with her kids’ activities, it can be tough for the mother of three — Mason, 13, Braydon, 11, and Tucker, 7, with hubby Mark Wilkerson — to stick to a meal plan. So the star partnered with SlimFast, whose products complement her on-the-go lifestyle perfectly. “If my kids are eating something I don’t want, like pizza or burgers, I can have a shake, and it’s satisfying,” says Hart. “It gets me through the night without any cravings, and I feel so much better the next day.” Here, she shares…