For centuries before 1954, running a four-minute mile was unfounded, and to many, ludicrous, perhaps irrational. After all, how could a mere human run so quickly? Could you picture a man in the 18th century openly declaring he would run this four-minute mile? He would be ridiculed. Notwithstanding the criticism and alleged "irrational" thought process, in 1954, Richard Bannister declared that he would break this four-minute mile paradigm. And he did. Since then, in the last 50 years, thousands of athletes worldwide have run the mile in less than Four minutes. Richard Bannister shattered the previous 500-year old societal thinking model.
How quickly physical results can change once societal thinking paradigms are altered and previously "irrational" thoughts are deemed "rational."
Today, if I were to say that I could run the mile in 3 minutes, would I not be the subject of ridicule, perhaps labeled "insane"?
If an overly-confident state cannot kill you, adopt it, as it is worth it's weight in gold. In the worse-case scenario, you have boldly lived and tried. In the best-case scenario, you could change the world.