My weakness would probably be lying to myself about how easy it will be to just hop back on the wagon. That lie comes in various forms. "You can just have a little bit like a normal person, and then tough it out." "You're in maintenance; what's a little junk food?" "Today's the last day of work before layoff, so you can have a treat as a goodbye and be strict while you're at home." "Hey, it's (vacation/holiday/a birthday/ an anniversary/a super moon/some other excuse, etc), you can take a break and get back to business later."

NOT.