In 2008, Jack was ousted from the company he cofounded (with Biz Stone, pictured on the right) by Twitter's board of directors but took the firing as a learning experience.
He revealed, "I was angry at the board, I was angry at my cofounders, I was angry at myself." But he explained, "I think I can be silent sometimes, which unsettles people a bit because they don't know what I'm thinking . . . The biggest thing I've learned is that I need to be more vocal."
Jack quietly returned to Twitter two years later, after he had already founded Square. He continues his efforts at both companies to this day.