Phineas Taylor Barnum (July 5, 1810 – April 7, 1891) was an American showman, politician and businessman remembered for promoting celebrated hoaxes and for founding the Barnum & Bailey Circus (1871–2017). Although Barnum was also an author, publisher, philanthropist, and for some time a politician, he said of himself, "I am a showman by profession...and all the gilding shall make nothing else of me," and his personal aim was "to put money in his own coffers." Barnum is widely, but erroneously, credited with coining the phrase "There's a sucker born every minute."Read about P. T. Barnum in Wikipedia
Constant hammering on one nail will generally drive it home at last, so that it can be clinched. When a man's undivided attention is centered on one object, his mind will constantly be suggesting improvements of value, which would escape him if his brain was occupied by a dozen different subjects at once.