In short -
I like to say "a fast miss, is still a miss and misses don't win gunfights."
In more detail -
I generally speak on this when talking about balancing speed and accuracy. I usually relate that accuracy has to be #1, in that if you can't hit what your shooting at no matter how long it takes you're screwed. This leads into the topic that if two shooters are equally accurate and can both put a single round into the tip of the nose of the other person, who would win that fight? Whoever can do it quicker. So with equal amounts of accuracy or precision, the person who can do it faster will win every time.
Keeping this in mind there needs to be a balance of speed and accuracy in a gunfight. This in turn goes into the topic of finding out where our balance lies and then pushing the shooter outside of their comfort zone, until they start to miss, or where the "wheels fall off", so to speak. From there we dial it down a notch and find an optimal point where the shooter should be concentrating their training in regards to what is an acceptable hit zone / percentage in conjunction with the speed requirement to get those results. Training at that "optimal" zone of balancing speed and accuracy the student becomes faster and more accurate with that correct repetition.
As the students time increases and accuracy / precision shrink, we then we increase speed and perhaps accuracy standards, or both. This leads into a shooter understanding that it isn't about being fast, for the sake of being fast, but being deliberate in their presentation and practice and with the deliberate and correct application of skills and then speed will follow. We don't teach them to be slow, as in "slow is smooth, smooth is fast", which is incorrect, but we teach efficiency in our motor skills which leads to increased efficiency and speed of repetition with correct practice increases.
If a shooters base fundamentals are not sound and if a correct training progression is not followed, a shooter can be fast as hell getting a shot off, but if you can't hit your target, you're screwed. Therefore the saying that I use is, "A fast miss, is still a miss and misses don't win gunfights."
On a side note to this one, we like to say that if you train for speed and your fundamentals are not sound you're also screwed. So I tend to say, "training to be fast but all fucked up, is only teaching yourself to be fucked up, very quickly."