That's what I tell students at Lark Camp. Each year, I teach a workshop called Get Your Voice Out of the Closet. I want to provide positive messages for nascent singers, and offer a foundation for harmony singing. We sing rounds, explore simple music theory, and discuss how to become singers.
I was lucky as a child - no one ever told me I couldn't sing. I truly believe that if we all sang as children, and no one ever said anything negative about our voices, we'd sing all the time. But the voice is a deeply personal thing, and the wrong thing said at the wrong moment can affect you for the whole of your life. The overtired chorus teacher who hasn't time to spare for a student who needs a bit more attention makes a comment like, "Maybe you should consider band." Parents - who themselves may have gotten negative comments as children - pass on the legacy of "we're just not singers in this family." The insecure classmate who feels competitive says something snarky to make themselves feel bigger. Take your pick; any of these are potent sources of frustration and anxiety about singing.
Once we've discussed that scary personal stuff, folks wonder if there's hope for them to become singers, and the answer is yes. But they'll have to work at it. It seems un-intuitive that you'd have to practice when speaking comes so easily, but singing requires as much practice as learning to play an instrument. In fact it's a lot like an athletic endeavor - you have to teach your muscles to produce controlled sound. This is the point in the workshop where someone inevitably says, "I want to sing like Norah Jones. Can I do that?"
Well, you don't get that job - Norah got that job. You get a better job: to learn to sound like yourself, like your most authentic self. You can learn to style yourself after someone you enjoy listening to, but like a fingerprint, your voice is yours alone, dependent on your lungs, your vocal cords, your experience. So you can't sound like anyone else, and they can't sound like you. Honestly, once you know you have no choice but to explore your voice as a unique instrument, it's quite liberating - and that's a pretty cool job to have!