Roger Bannister did something that many people had said was impossible.
He ran a mile in less than four minutes.
The thing is, he didn't accomplish this by running a mile as fast as he could.
He did it by setting out to run a mile in one second faster than four minutes.
Bannister analyzed the run, stride by stride. He knew how long each split needed to be. He had colleagues work in a relay, pacing him on each and every section of the mile.
He did something impossible, but he did it by creating a series of possible steps.
It's easy to get hung up on, "as possible." As fast, as big, as much, as cheap, as small…
The Bannister Method is to obsess about "enough" instead.