What is the deal with chocolate making you feel better with all the serotonin release the people talk about?

I don’t particularly fancy chocolate but let’s say I had a very bad day or I learned some piece of bad news today. Somebody offered me some chocolate (Heidi Dark 85% cocoa – don’t know much about chocolate but more cocoa it’s a good thing, that I know) and I ate half of it out of inertia. It just gave me a slight sickness state, I think the my serotonin is immune to this stimuli 🙂

So, I would like to know: does chocolate ever work? Does it make you feel good? What is about chocolate that makes people addicted (except for the sugar, of course)?