For Greek fashion designer Mary Katrantzou — whose unique take on textures, prints, and silhouettes in women’s clothing earned her international acclaim at a young age — confidence is the key to success. In an interview with “The Talks” in 2015, she admitted that doubts are natural for any artist. “In fashion you have to put a new product out there every six months with little time to process, little time to evolve, and all the ambition in the world,” she reflected. “It’s impossible, I think, not to doubt.” Yet Katrantzou also pointed out that we must believe in our own vision in order to create. It’s a truism even beyond the artistic world: When we move through life with confidence, we teach others to trust in us, too.

President Franklin D. Roosevelt led the United States through some of the most tumultuous periods in the nation’s history, including the Great Depression and the Second World War. He was also the first known President to have a significant physical disability. Despite those challenges, he implemented some of the most lasting labor reforms in U.S. history and helped ensure the Allied forces’ victory over the Nazis. His bracing wisdom continues to echo down the ages: We can take our doubts into account when making decisions, but we shouldn’t let them hold us back from moving toward our goals.

James Dyson could have been forgiven for slowing down when he was struggling to perfect his innovative Dual Cyclone vacuum cleaner. He made 5,127 prototypes before he got it right, but with every step he became even more determined. “There were 5,126 failures,” he said, “but I learned from each one. That’s how I came up with a solution.” It took Dyson 15 years of tinkering before his first vacuum cleaner was ready for launch, but no major manufacturer or distributor was willing to back the product. Undeterred, he set up his own manufacturing company, and soon his Dual Cyclone became the fastest-selling vacuum cleaner ever made in Britain. Today, Dyson is one of the wealthiest people in the U.K., with an estimated net worth of around $29 billion.