The head of the New York Stock Exchange explains the overlooked trait he sees in almost every great entrepreneur

Thomas Farley has seen countless entrepreneurs walk in and out of the New York Stock Exchange since he assumed his position as head of the iconic Wall Street institution four years ago.

So he has a pretty keen sense of what it takes to be a successful business leader.

The NYSE, the largest stock exchange by market capitalization, is the listing venue of some of the biggest companies in the world, ranging from energy giants like Chevron to global tech companies such as Alibaba.

Business Insider recently visited Farley at the New York Stock Exchange and asked him for his best advice for making it big as an entrepreneur.

He said there is one often overlooked trait, which he thinks is shared by just about every great business leader he's come across: Optimism.

"Optimism is a far more scarce commodity than people think," Farley said."The leaders who come through the exchange whether it's Johnny Chou or Alibaba's Jack Ma - are incredibly optimistic people." Chou is the CEO of Best, a Chinese logistics company that just listed its shares in New York.

Farley said the difficulties that underpin the process of taking an idea and turning into a successful business requires an unbridled optimism.

"When you are an entrepreneur starting a business you are going to encounter hurdle after barrier after rejection," he said."Ultimately to be successful you need to be optimistic."

"You need to see the world for what it can be, not what it is."

Farley, 41, got his break when Jeff Sprecher, CEO of Intercontinental Exchange Group, appointed him head of New York Board of Trade in 2007. In 2013, Intercontinental acquired NYSE Euronext, and Farley was named COO. In May 2014 he was named president, becoming the second youngest person ever to run the NYSE.