I received an email in my box from Mark Sisson who is the author of The Primal Blueprint diet/exercise plan. It doesn't matter what plan you follow, everyone slips. This is a particularly helpful email since weekends can be rich with slippage. I have edited his email down a bit, but here is what Mark wrote:
Look, I make no bones about the fact that the Primal Blueprint plan is technically a restrictive one. Since we're restricting only harmful or unnecessary foods and exercises, though, I'm also not apologizing for it...
The thing about restrictions is that people don't always pay attention to them, even when they know they'd be better off doing so - and especially when the things being restricted are cultural or dietary staples that we encounter on a daily basis. I liken it to a reformed heroin user vacationing in Amsterdam's Red Light District: temptation abounds... Imagine your temperamental supervisor goes out of the way to buy you an ice cream cake for your birthday... are you really going to turn down a slice?
Restrictive regimens invariably create issues for certain people. Issues like guilt, food obsession, and mania can rear their heads when someone slips up and eats the wrong thing. Even though physical or metabolic health isn't really impacted much from that single, isolated event, a person's psychological health can really suffer...
You eat a piece of bread at dinner and freak out to the point of being unable to enjoy your grass-fed ribeye. You eat that proffered slice of cake (because, who knows, a promotion might hang in the balance) and feel like you undid weeks of solid Primal eating.
Just realize that the Primal Laws aren't enforced by pain of death or injury. They are guidelines - solid guidelines that you should follow for optimum health - but they aren't uncompromising... Part of being human is "messing up" and rolling with the punches. To deny that basic inherency in pursuit of absolute 100% unrealistic perfection can actually be worse than giving in occasionally. You might even say that compromise is part of the Primal Blueprint.
But above all, don't panic! We've had people undo decades of metabolically destructive eating and exercising in mere months on the Primal path. There's no way a single meal of restricted foods throws you off. Just stay calm and get back on the horse. This isn't a crash diet designed to "shock" your body. There will be plateaus along with the descents, and for some, results come more slowly or gradually.
But results will come - mark my words - and slipping up once or twice won't really influence when or how they arrive.
Here's a pic of Mark Sisson and his wife, Carrie. Both are in their 50's.