First, I completely agree with you that it's incredibly easy to let your weight slip. Just wanted to add that I know many overweight people I have gone out to dinner with, or just been around, that consistently make the wrong choice everywhere they go.

I'm at a restaurant and order something made of say, cucumber lettuce chicken and whole-wheat bread(as someone who is about average weight) The people I'm with order beef patties with mayo on white bread with fries as a side. I just want to shake them and say stop hurting yourself!! But there's not much I can do when every time I give a healthy alternative they'll say yuck, give me the processed food instead.

So definitely don't be hard on yourself if your weight is slipping, but if you're eating out every day or eating high calorie foods, just try to replace some of those, even with something else unhealthy but less calorie dense.