Some ideas hurt: best and worst days

There is a lot to unpack in the concept of best versus worst day but I'll do my best to stay with the basic idea.
Young athletes have the impression that their best and worst days are poles apart.  Feel free to test this.  Is it reality though?  If we're gauging on outcomes alone then maybe.  Maybe?  No, not even then.  It just seems that way.  If we look away from an outcome and instead at the moment to moment behaviours and actions it is quickly obvious that not much is different from one performance to the next.  A win or personal best may contain a handful of well constructed moments but performances do not transform in the short or even medium term. 
The idea of a miraculous 'best day' is damaging.  It's simply not true and that's a problem all by itself.  A PB or win can appear as a new standard but what does that mean?  Any performance is a large collection of moments and a PB represents a higher than normal 'average' standard of execution.  It's actually not a requirement of a high performance standard that new physical standards are reached, only that the overall standard of work is high.  Exposing an athlete to the idea that they must become better than ever before is a very different kind of idea to executing better than ever before.  We are aiming for transformation in sport but it is not instantaneous and never miraculous.  Adaptation is a response to training and it involves immeasurably small improvements or differences over a long period of time.
The ultimate driver of progress is time, so our most important responsibility as parents and coaches and colleagues is to support ideas and attitudes and experiences that nurture and encourage participation.  Ideally, we need to prick the fallacy of competition as a transformative physical experience early on.  For the same reason it cannot transform, competition also cannot destroy.  We need to take the time to explain to children that there are no catastrophic days.  Certainly we can have catastrophic experiences but the greatest driver of these are emotional responses to the disappointment of not achieving what are, if we think about it, unreasonable expectations to begin with.  If we train well and keep practicing it is just a matter of time until we execute better than ever before, and just a matter of time also for our tools to grow and evolve to higher levels.
We all need good days, and proof or evidence also that progress is occurring but first we need to understand what this 'proof' is and what it's not.