How's your mindset when you start singing? Are you critical of yourself or do you treat yourself with kindness? Sadly, we often reserve our best encouragement & constructive criticisms for our friends while we beat ourselves up.
I'm here to tell you that this strategy isn't helpful. You're never going to improve by being awful to yourself. I think of the Phantom in Andrew Lloyd Weber's Phantom of the Opera. He's the worst voice teacher ever! All he does is yell "Sing! Sing for me!" at Christine and expects her to bring her best performance. Would you pay someone for that? (please say no. If that's all your voice teacher does, please message me now)
Today I'm bring you some affirmations. When you find your inner voice being hard on you, intentionally replace that negative voice with one of these simple thoughts. Repeat it to yourself until you believe it. Because whatever you tell yourself becomes your truth. Say, "I can't" often enough and you get to be right.