Find a way to make yourself worse off if you cheat. One idea is to hand a large amount of cash to a family member or friend. Nominate something you hate to give the money to if you cheat. We will do more to keep £/$100 than we will to earn it, it's a sales technique.
Write your goal. Give it to the family member/friend along with the cash. If you fail, you lose the cash. Simple/hard as that.
Hopefully you'll get other ideas from other members. Good luck.
Why use a sledge hammer to crack a nut when a steam roller is even more effective, and, is fun to drive.