The No. 1 trick I always teach to build unshakeable confidence—it worked for Beyoncé and Adele

When Beyoncé walked on stage early in her career, she didn't do it as Beyoncé. She became "Sasha Fierce" — an alter ego she created to cope with nerves. The strategy behind it can work for the rest of us, too. As a therapist for nearly 25 years and the author of "The Mental Strength Playbook," I've watched smart, capable people choke under pressure. They stumble over sales calls even though they've memorized the script. Or they stay quiet in meetings even when they have the best idea in the group. No matter how talented or prepared you are, self-doubt can hold you back. I teach clients to channel an alter ego because it's one of the fastest ways for them to move past it and perform at their best. What an alter ego actually does for you When self-doubt hijacks your brain, you start thinking about everything that might go wrong, which distracts you from the task at hand. Your first reaction might be to talk yourself out of feeling nervous. But that often backfires and makes it even harder to keep your head in the game. Channeling an alter ego instead is like stepping into the mindset of someone who doesn't get nervous. "It's kind of like when I do a movie, becoming the character, [and] once you put on the wig and once you put on the clothes, you walk different," Beyoncé told Oprah in a 2008 interview . Though Beyoncé said a few years later that she'd retired Sasha Fierce as a separate persona, there was a time when the alter ego would show up whenever she performed. …