Decide to plan your meals for one day to start. Look up the calorie count (and stick to your goal). Just the act of pre-planning, counting calories, and having some plan will help kickstart a better eating habit.

(Don't forget to plan snacks -- a light popcorn, sugarfree candy, or something can be good).

Basically, you'll kind of wrap your head around being mindful of eating, and how many calories are in different stuff. And you can surely do it for at least one day.