my experience with dieters is that they dont commit, and when no one is around tend to 'cheat' but rationalize and justify it somehow.
it is very difficult to do though, i understand. when i switched from your average american fast food type diet when i was 19 over to a health conscious, all natural wholesome foods type thing it was hard. i relapsed quite a few times in the beginning. it supposedly takes two to four weeks for a person to get used to a new diet or lifestyle habit/change in general.