Failure.

Remember when I said I really like red wine? Yup. I drank some. Even though I was trying not to. Oops.

But, instead of beating myself up over it I’m going to rip myself up over it.

...what? 

I did something I said I wasn’t going to do. So, that’s a failure, right?

Ahhhhh grasshopper, but failure has another definition in the fitness world. If you’re a fitness noob, failure in the gym means picking up a heavy thing and repeating picking up that thing until your body literally just canNOT anymore. That is an incredibly unscientific definition.
Here is a much more eloquent one, in case you’re into that:

Definition: Muscle failure refers to lifting weights to the point where a muscle can no longer contract concentrically. If you're a bodybuilder, powerlifter or involved in competitive strength training, lifting to momentary muscular failure may be part of your training. For the average exerciser, you don't necessarily have to lift to complete failure to increase strength and see results. Make sure that you lift a heavy enough weight that you can ONLY complete your desired number of reps - the last rep should be difficult, but not impossible and you should be able to finish the set with good form.

If you repeat an exercise “to failure” it basically confuses the shit out of your muscles that are used to doing said exercise a comfortable number of times. They get all like whatthefuckisthis?! ... and in response they get all ripped up and then they have to change and grow to accommodate the new activity.

(...you see where I’m going with this yet?)

So what I decided this morning is that every time I have a “failure” in my life (like the wine, or if I decide to eat something that’s delicious and terrible for me, whatever) the next day in the gym I’ll repeat all of my regular exercises to failure.

Thus, using my failures to make me stronger. Literally.