Monday: "Ok, that wasn't too bad." Tuesday: "Ok... I did it." Wednesday: "I'm feeling kinda weak..." Thursday: "Ugh..." Friday: "I feel bit better today." Saturday: "Phew... almost a whole week!" Sunday: "I did really good this week, I'll eat this entire pizza and chocolate cake to celebrate."
Next Monday's weight the same as the last. You got literally no where because of a pizza and cake. I can't tell you how many people can't make it a week without fucking it up.
So, as far as counting calories, just remember to count your cheat meals and see just how many days and walks they are reversing. Suddenly, they won't be worth it.
Just stay consistent. You will have to go a bit crazy fighting hunger pains. You will tell yourself no thousands of times and your mind will try and rationalize every single extra bite or meal. Fight it. Every single time. Never let it win. Not once. Because once is all it takes. It gets better after about 3 weeks, but there will always be temptations.
Then 6 months later when you've changed and feel like you've got this? Go 6 more months just to keep yourself in check. Ween off the diet very very slowly. Exercise too. Never go cold turkey on heavy exercise routines.