I totally agree with your way of looking at things. Having an "off plan" day every once in a while is NOT the end of the world. Like you said, it's called life!
I have a St. Patty's day party coming up...green beer and pizza! While I've had a few "oops" days here and there, I'm usually at least right at, or maybe a few calories over the high end of my budget. I have a feeling St. Pat's day will probably be over 2,000 calories when all is said and done. (I have not eaten more than 1,750 or so calories in a day since I started my plan.)
But you know what? It's ONE day, and unlike the way I used to think about "dieting" in the past, this is not going to "undo" all my progress and it's not going to derail my whole plan. No matter what, I'm going to keep going!
So good for you. It's all about being flexible enough to let life happen, yet still keeping things under control. You're doing just fine