If you can't focus, fix it. If you can't fix it, don't lift. Find another sport that requires less of your mind and body connection. Ultimately, it is wise to train at a time or on a day when you can mentally support your lifting. We often have good intentions as we prepare to lift and seldom need to exercise restraint.
Lifters generally condition themselves to perform on schedule.
Therefore, we need to master the ability to recognize the times when it is not prudent to train and develop the skills of exercising control and sound judgment. The lifter who does not hear or treat her inner voice with respect is far weaker than one who listens and makes sensible, appropriate adjustments. My back is fine. It was only bruised, like my ego. I was given the opportunity to re-learn a very important lesson that no amount of accumulated experience can compensate.