Will I be among those who have mixed a righteous deed with an evil one, or will my good deeds be annulled, according to the Prophet's saying, "But they are a people who, when they are alone with Allah's prohibitions, violate them"?

One must cultivate awareness of Allah Almighty's constant observation and His knowledge of the servant's actions. Nothing is hidden from Allah, and your secret is manifest to Him, as He Almighty said: "And you do not perform any deed except that We are witnesses over you when you are involved in it" and "He is with you wherever you are." Ihsan (excellence in worship) is to worship Allah as if you see Him; and if you do not see Him, then [know that] He surely sees you. So, beware of persisting in sins in private, lest you become among those whose deeds are rendered fruitless.