According to Osho, sincerity means living from your own inner light, not from the borrowed dictates of parents, priests, or politicians. It starts with meditation, which reveals that light, and then courageously acting from it. Such authenticity creates integrity and freedom, even if it brings conflict with society. Imposed moral codes breed hypocrisy; true virtue flowers when you follow your own awakened awareness.
Sincerity is listening inside and doing what truly feels right to you, not just copying others.