A pound of new muscle will enable you to burn 75 more calories a day. Most of the fat burned in your body is burned by your muscles, so if you aren't building your muscles up, you're getting in the way of your own natural ability to burn fat and lose weight.
Giving up chocolate is very difficult when dieting and it is one of the things that many people end up eating when they cheat. There is no need to give up chocolate, you just have to watch the type you are eating and the amount you consume. Switching to a dark chocolate saves a lot of fat and calories.