Why do we make our body addicted?

Trying to stay clean from sugar is harder than I imagined. I thought the first weeks would be the toughest but I had wrong. A few weeks into it and NOW it's the time when I feel my sugarcraving for real and nothing helps. I thought the worst part would be gone by now. When I was younger I could stay away from sugar for years, believe me, but I don't know how I did it. (Penny) says it's all about balance and maybe I should go with the flow for a while, just for a day.