It's easy. You don't have to do anything. Just do nothing

Here are three things to keep in mind to eating when you shouldn't: 

1. Food doesn't jump into your mouth. It's not going to attack you or come after you. It's just sitting there. It requires you to actively pick it up and put it in your mouth. It's a conscious decision you make. 

2. Eating is a habit. You only want to snack because you're used to it.

3. Don't compensate if you slip up! Maybe you had a cookie too much (in fact, every cookie is a cookie too much), don't restrict more the next day if your diet is already restrictive! It'll turn into a circle effect and a race against yourself. 

<-although this girl is skinny fat. 

                                                                   You can see bones and a bulge on her                                  stomach... It looks like she starved herself. Not sexy.