Regarding relapsing, I know where you're at, and it is scary. As someone who handled it poorly, here's my perspective:
I had lost 110 lbs but got to the point where eating "perfectly" was just not something I could do everyday. I've read that it's normal for willpower to get harder over time, not easier as one would think. At first, the cheats were minor - just the kind of thing one might eat on maintenance, and I was not all that unhappy about maintaining for about 4 months. But, slowly, it slipped into the old bad habits and I regained a lot.
If I get to that place again, here's my intention: I'm going to accept that I need a break from deficit calorie eating and that I have a taste for things that I haven't been eating. I'll allow myself an extra 300-500 calories, and plan in the cheats. The last four words are the critical ones. Plan.In.The.Cheats. In other words, keep tracking, make the nutrition still good, but do maintenance eating until I feel like working again. My hope/guess is that my mind and body will thank me by being ready to drop the pounds again by then. And by planning, I won't be in that loss of control, anything goes mind set that is a killer for me.
That was then:
November, 2008: 315 lbs
November, 2009: 215 lbs
May 28, 2011: 254 lbs
This is now:
July 24, 2011: 237.5 (-16.5 lbs)
October 12, 2011: 222 (mini-goal)
September 1, 2012: 145 (goal)