When you think or talk about making lifestyle changes do you feel or say you have to do certain things? If this is the case there is a feeling associated with having to do something. Feeling obligated can put you in a defensive mode and make you not want to do it. Where as if you tell yourself and think in terms of choosing to do it you will cut down on the guilt.
So for the next week analyze your thoughts. Change your tune to choosing instead of having to. You will see great changes in your behavior.