I believe in God, I believe in The Beatific Vision, yet I can't prevent myself from eating an extra amount of chocolate. I try to convince myself not to eat it:"God will be displeased, you will be less dear to Him"
Remember first of all that all of us, excluding a miracle ability, must eat.
Now it is natural for us to eat good food, and very hard for us to only eat plain and especially disgusting food. So naturally there is a very strong inclination to eat chocolate, and that can be come disordered into an excessive desire for it.
I have a problem with coffee. I was able to stop drinking after a couple of days of headaches, then I started drinking again, and haven't been able to stop. The problem I think, is that I still think I must have it to energize myself.
My confessor told me something very important, he said:
"We can do nothing good without God."
We cannot overcome inclinations towards evil without grace. Now, in order not to eat chocolate, you must put yourself in a position where there is none available. When I run out of coffee beans, I will not buy any more, that is part of my plan to quit drinking coffee. To quit smoking or drinking, the most important thing was to get rid of the tobacco and the liquor.
Secondly, you must develop good habits. Every day you should only eat at fixed times, and develop a good idea of what you will eat at each meal. First set a goal for each meal. If you find it is not sufficient, you may adjust slightly the amount you eat at each meal. Hopefully you will be able to develop the habit of only eating what you should eat. Every day must be practice. Try to fast when you are able. This will help to build discipline. And pray for grace, because without grace it is impossible to do anything good.