If you want to sabotage someone’s good habit, introduce a little doubt about it into their mind. It is amazing what a little doubt can do – it can make turn a hard uphill battle to sustain a good habit into an impossible task.

The resistance inside you is looking for anything to grab onto, anything to keep you from doing what is good for you. Be wary of anything that exists solely to introduce doubt – for example, studies sponsored by a group that benefits from your doubt – and be careful about the doubt you introduce to the people you care about. It has a much bigger impact than you’d imagine.