Nothing more. Nothing less.
Let's say you're prescribed to do something for 10 reps. Like sprint a staircase, then walk back down; repeat 10 times.
Well you may rush through them, focused simply on getting all 10 reps done, even though the number "10" is much more arbitrary than personal. Quality or approach may suffer.
How about instead, you do just one repetition - just one sprint up the staircase? You do it as if it is the one thing existing in time. Just one. Then you walk back down, to do perhaps "just one", again.
In this "just one" mentality, attention to detail, and passion, have a chance to thrive (let alone survive).
Maybe you do only four sprints. But they are of the kind which make them worth way beyond 10 shitty ones.
Or, under the sky of "just one", you may without knowing or caring do 13 lovely sprints - each of them containing the magic of presence and spunk.
The point being, if you set or limit yourself to an arbitrarily placed number of repetitions, you will begin to lose the brilliant capacity in you to listen, to feel, to let the energy of what is contextually appropriate move you along naturally. True progress will be halted if numbers or outcome hold power over process.
So how about "just one"? Always Just One.
The acronym for Always Just One can be #AJO (pronounced "Aye Joe!").
The AJO perspective can be applied to the number of sets you do for an exercise, too.
You may also want to consider something called The Law of Diminishing Returns. This "law" says that at some point during the experience you may notice you're not dashing with as much strength or speed as you were in previous reps or sets. If you continue to do more sprinting after this point, then your "return" (in other words your training effect or adaptation) may not be much better than if you merely stopped. Just food for thought which you can digest; or regurgitate, because you certainly have the prerogative to keep going regardless of any supposed "law".
And to summarize the bulk of this post:
"Don't Count Your Reps, Make Your Reps Count" ~ Nick Garofalo