Here's a few tips I read in a health magazine about how to trick your brain into eating less.
1. Cut your food (or treats for this matter) into smaller bit sized pieces, to make it seem like you have more than you do. A candy bar cut into several pieces may trick you mind into thinking you are getting to enjoy more.
2. Eat without distraction such as the t.v. Eating while watching a show will take your mind out of the eating experience and you might not realize you are full. If you take notice of how you feel while eating, by not distracting yourself, you may not eat as much.
3. Keep treats out of your house so you won't be tempted to want them. If you must have them (I do often) then keep them put away so you don't want them all the time.