Jennifer Garner’s lips are zipped. The toughest part of parenting for the actress has been allowing her and Ben Affleck’s three children — Violet, 18, Seraphina, 15, and Samuel, 12 — to make decisions by themselves. “I have a really hard time not saying, ‘This is what I see you as,’ and, ‘I think you should,'” the “13 Going on 30” star admitted to People in an interview published Thursday. “I really have to sit on my hands.”