People reports that Chiefs star Travis Kelce just attended his 13th performance of Taylor Swift‘s The Eras Tour, and the significance of that number is lost on no one.

Swift is a big fan of the number 13 — so much so that before every show she paints a 13 on her hand for good luck. Why are those digits so near and dear to her heart?

Swift was born on December 13, 1989, and explained in an interview with MTV News: “I turned 13 on Friday the 13th. My first album went gold in 13 weeks. My first No. 1 song had a 13-second intro. Every time I’ve won an award I’ve been seated in either the 13th seat, the 13th row, the 13th section or row M, which is the 13th letter. Basically, whenever a 13 comes up in my life, it’s a good thing.”

Swift isn’t the only one who leans into superstitions to give herself an extra boost of confidence. In the book Recipes for Good Luck, author Ellen Weinstein researched the superstitions and rituals of some of the most famous and successful people in modern history. And while some might seem odd or silly to others, Weinstein writes that beliefs, rituals and routines can “help you face the world with ambition and confidence and inspire you to go on making good luck of your own.”

Here are some other superstars who used pre-performance rituals to get ready to go.

• During his playing days, NBA superstar Michael Jordan wore UNC shorts underneath his Chicago Bulls uniform. They were the same shorts he wore in 1982 when he scored the winning jump shot that brought his college team, the University of North Carolina Tar Heels, their first NCAA championship since 1957.
• Tennis great Serena Williams has several distinctive pre-performance and on-court rituals: before a match, she’d tie her shoelaces in the exact same way and always bounced the ball five times before her first serve and twice before her second.
• Before beginning the opening monologue of her former talk show, Ellen DeGeneres would be sure to throw a mint in the air and catch it in her mouth.
• Rihanna has said that she doesn’t allow anything yellow in her dressing room before a show, believing it is bad luck.
• Soccer legend David Beckham has a thing against odd numbers. His wife Victoria told The Chicago Sun-Times that their house had several refrigerators, each devoted to different types of food. “In the drinks one, everything is symmetrical,” she explained. “If there’s three cans, he’ll throw one away because it has to be an even number.”