If the carrot doesn't work, it's time for the stick. Instead of rewarding yourself for meeting your goals, pay an "anti-charity" money when you cheat on your resolutions.
An anti-charity, according to Forbes, is any cause or issue that you are vehemently against. Once you find that, force yourself to donate to that cause whenever you fall short of your goals. Find a friend to hold you accountable or use a web site like Stickk.
The idea draws its roots in a study that suggests people are more loss-averse than reward-oriented towards goals; i.e. when it comes to motivation for resolutions, people would rather not lose something than gain something. For the anti-charity system to work, the issue can't be something you are mildly offended by, it needs to be a hot-button topic that sets you off. Everyone has them, it's just a matter of finding yours.
Of course, if this seems too extreme for you, there are other ways to stick to your resolutions.