It sounds like you understand the problem, and I've also had probelms with over-eating when I've got too much time on my hands. What I find helps me is that when I get stressed, or bored, or any other situation where I would tend to overeat... I now go out for a 20 minute walk and listen to Jimmy Buffet music [obviously feel free to replace Jimmy Buffet with whatever relaxing music you would like to listen to]. It's relaxing and it's easy to do.
Good luck tomorrow! Remember to do your research on the company (i.e. read the financials, think of some good questions to ask the people you are meeting with, read the recent news about the company, etc.). Be confident and sell yourself!