Hawzah News Agency – Imam al-Sadiq peace be upon him says:

المؤمنُ بَينَ مَخافَتَينِ: ذَنبٌ قَد مَضى‏ لا يَدْري ما صَنعَ اللَّهُ فيهِ، وعُمرٌ قَد بَقيَ لا يَدْري ما يَكْتَسِبُ فيهِ مِن المَهالِكِ، فهُو لا يُصْبِحُ إلّا خائفاً ولا يُصْلِحُهُ إلّا الخَوفُ.

'The believer lies between two fears, fear of a sin that he has committed in the past and does not know what action Allah has taken [with regards to it], and fear for the remainder of his life in which he does not know what destructive sins he may commit, therefore he always wakes up in the morning fearful and it is only fear that reforms him.'

Source: al-Kafi, v. 2, p. 71, no. 12