Lots of us consider repetition to be backsliding. "Last time I ran this route I was five seconds per mile faster!"
But how did it feel? Maybe this time you did it with less rest, less effort, a stronger form, and shorter recovery time. Maybe you just had more fun.
If you're revisiting the same musical piece you played several months ago, perhaps it is now smoother, more fluent, and more confident.
Even when you compare apples to apples, you might not be considering all the variables.
Of course, even if there is truly no change in your position or ability, the how is still what matters. You always have control over the most important aspect of it: your attitude. And sometimes that's all you can control.