I'll try to show my sympathy first, validating their feelings, and then process to lift up their confidence. No one is perfect, and everyone has their own flaws. It's okay if you make mistakes or such, because it means you're brave enough to try and learn. Your mistakes and your failures don't define you. It's okay to feel sad and disappointed in yourself, but don't let yourself drown in it for too long. Get up, pick yourself up, and keep learning. Live your life to the fullest.