This wont be the most popular opinion, I'm a bit more strict with diet and my students diets. I believe people are typically addicted to junk food. Would you let a drug addict have a little bit of drugs every now and then? Same with sugar addictions in my opinion. It works well. People don't care for it after it's gone long enough because they never get reminded of it.
That said, cocoa isn't bad. It's the crap they put in it. But I'm currently enjoying some dark chocolate now. Instead of biting it, try grinding it against the roof of your mouth. It taste less bitter.