More than anything else, Elena, the shift in mindset that will make the biggest difference for you is around freedom of choice. As you say, “often during my day I am trying to say no to things before the situation comes up. Restriction on many things.” And you feel relief with the thought that your choices are always open to you in the future. This is very good; it is the light at the end of your tunnel.
Your description of the sensations of desire are nothing other than symptoms of your denial of choice: inner fight, nervous, restless, rebellion, unfairness. It would be good for you to continue to look for the sensations of desire, rather than your prohibitive reactions to it. It may take a while for you to grasp this.
It’s also worth noticing that your restrictive/prohibitive mindset around food is not confined to this particular problem with overeating this chocolate. The image I get is that you prohibit (successfully) all day and maybe for a few days, and then go into rebellion with this particular item. Yes?
Yes, it is frightening to open up to a genuine freedom of choice, but only if you are unable to manage desire. And you find it tough to manage desire when you don’t feel free to overeat. It’s a vicious circle 🙁