I find that I go phases of 'eating very well' and phases were I dont really eat badly but where I eat more mindlessly, I think it's something that you just have to work on. I read a brilliant quote somewhere that really stuck with me and helps spur me on "We are what we repeatedly do, Excellence therefore, is not an act but a habit".
You've done an incredibly good job by the way and you seem to have such a positive attitude that I'm sure will carry you through the rest of your loss and into maintenance.