agree that its about doing it unquestioningly. I take the dogs for a walk everyday. Its hardly the best exercise in the world, but 30-45 minute walk is enough to help. The moment I question whether I can be bothered to take the dogs out though, I don't, and then it gets harder to do so next time. This morning it was cold and dreary and I didn't notice so I didn't bring my coat when I came downstairs. I knew if I went upstairs for my coat (therefore diverging even slightly from the habit) and I would find some excuse not to go. Maybe quickly checking my email or something. So I came back from my walk cold and wet rather than not go at all.