Earlier this summer, I read the book, The Four Agreements, by Don Miguel Ruiz. After all, it's Tom Brady's favorite book. I promise, I'm perfectly capable of reading a book and not thinking about how the author's message applies to strength training (I swear). However, Ruiz's 4th agreement is the perfect advice and mindset that we should adopt heading into our own strength training workouts: Always do your best.
It's as if he is actually talking about our workouts when he states:
"Under any circumstance, always do your best, no more and no less. But keep in mind that your best is never going to be the same from one moment to the next. Everything is alive and changing all the time, so your best will sometimes be high quality, and other times it will not be as good."
Applied to our workouts, we cannot expect that on each and every day we will be in the same physiological state. Our sleep, hydration, job stress, nutrition, and a host of other factors will fluctuate from day to day and workout to workout. And therefore, our performances will also fluctuate. Regardless, the mindset we must adapt is: Always do your best.