I absolutely know how you feel. I do the same thing to myself. The minute I reach a new low weight, something seems to snap & suddenly I want to eat everything that I've made "off limits" during my weight loss efforts.
So, I think the challenge for us isn't actually one of self-contol. I think it is one of deprivation. We clearly feel that we sacrifice & deprive ourselves to get to whever we are going. So to combat this, I am working on factoring in some of those "off limits" foods with regularity. Probably not every night, but a few times a week? That way M&M's aren't actually something I cannot have, but instead, something that is on plan - maybe not today, but maybe tomorrow. Know what I mean?
Don't beat yourself up. It is hard when you have company in town. I never want to be viewed as "different" or make anyone uncomfortable. You feel how you feel - I can't say anything to make you feel differently. But feelings are not always to be trusted. When I make self-defeating statements to my therapist, she always says something like "That is one thought. Have another one." It seems so simple, and at first made me a little angry. But over time, it has really stuck.
Maybe it will help you, too.