Umm al-Mu'mineen Aisha Siddiqa (may Allah be pleased with her) says that the Messenger of Allah (peace and blessings be upon him) would abandon a deed, even though he loved it, out of fear that people would act upon it and it might be made obligatory upon them. And the Messenger of Allah (peace and blessings be upon him) never performed the Duha prayer, but I perform it.