Imposter syndrome at my new job is eating me alive

I got hired for a role I wanted for years, and instead of feeling proud, I spend every day waiting for someone to realize they made a mistake. I over-prepare for everything, stay late to double-check work that's already fine, and deflect compliments. My manager said I'm doing great. I don't believe her. I keep comparing myself to colleagues who seem effortless. I know imposter syndrome is common. Knowing doesn't make it stop. What actually helped you feel like you belong?