I have had the same experience myself several times over my life. I have gotten to (or very close) to my goal weight, and then stopped all the good habits and relapsed into the bad habits. This may sound stupid, but in my mind at the time was the following reoccurring thought: "Well, I am thin now, so I can eat whatever I want", which of course was a bad way of thinking.
I also think that I sabotaged myself, because as I got closer to goal, everything that I thought was going to happen to me when I got thin (popularity (high school), the guy I had a crush on would drop to his kness and ask me to marry him

, Harrison Ford would realize I am his soulmate

).
Seriously though, when I got to goal and nothing "magical" happened

I was a little disappointed. I am not saying my thinking was logical or was correct, but that was my feeling at the time. Now that I finally recognize what is going on, I can change my thinking and not do the self sabotaging that I have done in the past.