In January of 2013, Mike Lewis sat in his cubicle on the 39th floor of the John Hancock Tower. The office at Bain Capital was mostly empty for the night, leaving just him and his friend in the next cubicle over. Lewis knew that banking wasn’t where his passion was, but he feared the judgment of others if he pursued the dream he’d had since he was 10 years old: playing professional squash.

Five years later, Lewis stood in front of a crowd at Harpoon Brewery in South Boston to discuss his successful book “When to Jump,” his international tour playing squash, and the friend that encouraged him to chase his dreams.

“When to Jump” chronicles the experiences of 44 people who decided to make radical changes in their lives — or, as Lewis puts it, decided to “jump.” Whether it be starting a company, having a child or deciding to switch careers, Lewis compiled the stories that he hoped would provide inspiration for future jumpers.

“It’s helpful to see that there’s a new way to consider careers,” he said. “The book serves as a sort of permission for people to go do what they love.”

Lewis spent Tuesday night promoting his book’s message at the sold-out Boston stop of his tour, recounting his story as guests sipped award-winning drinks, chatted and ate bottomless homemade pretzels at Harpoon’s beer hall.

“It’s amazing to have people bring not only themselves, but also the most authentic version of themselves and share their jump story with everybody,” Lewis said.

Many patrons came not only to hear about Lewis’ book, but also to support the Corey C. Griffin Charitable Foundation, which sponsored the event. Corey Griffin, for whom the foundation is named, was Lewis’ main supporter when he was still debating whether to take his jump from Bain Capital.

Griffin worked beside Lewis, and, when others discouraged Lewis’s non-corporate dream of playing professional squash, Griffin wholeheartedly supported him. He also provided nothing but optimism for the early stages of Lewis’ initial concept, which would later become “When to Jump” in its novel, podcast and blog forms. Lewis later dedicated the book to him.

“I think my brother in a way was always a dreamer. He always followed his passions, and his passion was charitable giving and lifting up others when they were in need,” said Mike Griffin, Corey Griffin’s brother.

Mike Griffin, 29, of the South End made it his mission to continue his brother’s charitable work after his brother’s death in 2014. The foundation helps underprivileged children receive education, health care, mentorship and other advantages. At the event, Griffin moderated a panel featuring Lewis and two other jumpers, Dan Kenary and Laura McKowen.

Kenary, 57, of Wellesley co-founded Harpoon Brewery after leaving a career in banking. He said that while the experience was initially terrifying, it was ultimately gratifying and exciting. His brewery, now 32 years old, has two locations, various awards and even branded merchandise.

“It wasn’t in our family background to take risks like this and start new things, so once I did it, it really felt liberating,” Kenary said. “If you have a dream or a passion or a curiosity, follow it. Nurture it, follow it, and don’t be afraid to take that leap, take that jump.”

McKowen provided a non-business perspective: overcoming her alcoholism and moving into a life of recovery and positive blogging. She said there didn’t need to be a grand plan in the jumping process, and that more personal motives were also valid and rewarding.

“I wasn’t going to waste any more time,” she said. “I wanted to show my daughter what it looks like to chase your dreams.”

The panel closed with audience questions, after which guests had the opportunity to purchase Lewis’ book and get it signed. Many continued to drink the two free beers included with each $30 ticket as country music artist Timmy Brown performed.

“It’s great to get so many powerful personalities here,” said Chris Steele, 28, of South Boston as he held his newly purchased copy of “When to Jump.”

Although Steele himself hasn’t personally jumped, he knows many who have, and found the event to be “encouraging and empowering.” He also came to support the Corey Griffin Foundation.

“The big vision was never just a book; it’s really a messenger for something bigger,” Lewis said. “This is a book that champions the everyday person.”