Well setting rewards for yourself is one way but here is an alternative I heard about...

stickK ? Change Starts Now

You have multiple options on this site but one of them they are best known for is the stick...if you opt to give your credit card info they can give money to a an anti-charity of your choice at a time point an value you specify. So you pick a group you hate that it would absolutely pain you to support and that is your motivation. I wouldn't pick something so horrible as the KKK just in case I screwed up from time to time but I think the Republican Party might still be horrifying enough to keep me in line....of course given politics vary you can pick whatever you consider awful and complete your goal to prevent donating to them. It's a pretty strong motivator.