It's always easier to say "I don't want that", when it comes to eating fast food, pizza, chips, etc, than it is to say "I can't have that". Saying "I don't want that" gives you control of your diet, instead of your diet controlling you.
Typically, when a craving hits, if you can hold off eating for 10 minutes, the craving will go away. Another thing to remember is like Bri said - the pleasure from eating a food only lasts for a few minutes. If you're going to eat that food - say a small piece of chocolate - you should sit down quietly and savor it; if you take time to really enjoy it, you'll feel much more satisfied than if you gulp down a great big piece that you barely took time to taste.
Here's a thread I posted a few days ago, so we could all kind of get to know each other... you're all free to post your situations on it, so others in the forum can get to know you...
http://www.medhelp.org/posts/Weight-Loss--Dieting/Welcome/show/2119291