I'm like this too! I think "Oh, I haven't had THAT many calories today!" And then I log all my food, and I'm wayyyy over my "limit."
The one thing that keeps me in check is logging things AS I EAT THEM. Then I know where I'm at for the day, and how many more calories I can "afford" to eat. If I log them at the end of the day, I always have a terrible surprise waiting for me.
I try to give myself a calorie allowance, and I can only spend that many calories a day on food!
SW: 176 (ehh...we'll go with 05/01/10)