Mental thing is a tricky business. You just have to prepare it to put down the snack. It's only 5 pounds now, however, you need to act right away before it became 10, 15, ... I am totally regret to let myself loose too long. there are a few things I try when you want to snack.
1. Chew gum if you want to chew something
2. take a walk if you can
3. drink something that have no calories (tea work for me)
the list could go on and on, but the main thing is get your mental stuff together and get down to business.