He is the All Seeing, the All Hearing. There is nothing on this earth that occurs without His Knowledge. He is aware of any secrets that you may have, even if you try your hardest to hide it from everyone else. He knows the condition of your heart, the sins you have committed and it is all recorded.
“Does he not know that, when the contents of the graves are poured forth, and the secrets of the hearts are made known, on that day (they will find) their Lord is Well-Aware of them.” ~ [Sūrah al-`Ādiyāt: 9-11]
On the Day of Judgement our actions will be revealed for all to know, so turn to Him in repentance and hasten to perform good deeds while you still have time on this earth.