I generally find that it takes less willpower to execute a plan that I've already made. I set aside a little time every morning, and a longer period every Sunday, to be effortfully strategic and come up with some specific next actions that I can mindlessly execute for the rest of the day/week. I think this is more or less standard GTD (although I've been iterating on my personal system for long enough that I can't really remember exactly what David Allen describes).

I agree that separating 'planning' and 'doing' like this works especially well for doing aversive things. Your 'planning self' doesn't have to worry about actually doing anything, and your 'doing self' just has to trust your planning self.