Making you prize and punishment (and the “what for”) public (even if you stay anonymous) might help you abide by it. Because it’s public, people can and will react and encourage you.
A site where you publish you goal, your carrot, and your stick. As time goes by you update your post with your progress, when you deserve your carrot, when your stick, and whether you actually received them. People can comment, encouraging you or criticizing you when appropriate, to help you achieve your goal.