An excellent point!!
Tyler's post above sums up my experience exactly... there are times, when I feel tremendous success and progress, and other times, when nothing is seemingly happening, and it does not appear to DIRECTLY relate to anything in particular, including my diet choices...
and just to clarify, I eat generally quite "sanely" and healthy, but then there are moments, when I just HAVE TO go and get a piece of chocolate or a cookie, and yes, I know I should not be doing it, but I am anyway, just because that is (seemingly :) the only way to keep my sanity...
I like the idea of "non-linear" cycles, and as long as there is an overall progress, that is all the encouragement that I need to continue.