Perspective. Sometimes you've got it, sometimes you don't. If you're lucky, you have people in your life who can provide you with a little extra help in that area when you need it.
A little while back, I was discussing with a friend how I'd been somewhat lax with my eating that week. Eating some unplanned grapes. A raisin here or there. And, for at least 3 days in a row - having 30 almonds instead of my planned and accounted for 20.
She stopped me and asked me to think about what I had just said.
Now, she was in no way condoning the deviation, merely pointing out that in the grand scheme of things, 10 almonds is not much of a deviation.
The issue itself lies not in what was eaten or how much, merely in the fact that it was done mindlessly. Not because I was starving, or lacked energy, or even because I was DYING for another almond. I ate 10 extra almonds because they were there, so why not? I ate the grapes because they were sitting out on the counter, about 5 feet from my desk. The raisins because they had fallen out of some cookies.
How many times have you bailed on a workout and kicked yourself in the ass for it? Before you beat yourself up though, examine WHY you bailed. Were you stressed at work or at home, over-trained, sick or ridiculously tired? Or were you simply not in the mood?
Taking an unplanned rest day is OK. Listening to our bodies is smart, no question about it. Having a flexible approach to your diet can be a great thing as well, reminding us to enjoy life and keeping us from psychological burn-out.
But when these moments arise, we need to take a moment to step back from the situation and examine the motive behind the behavior. Be truthful and you will never steer yourself wrong.