If the believer were to know what is with Allah of punishment, no one would hope to enter Paradise, and if the non-believer were to know what is with Allah of mercy, no one would despair of entering Paradise. [Muslim]

"«لو يعلمُ المؤمنُ ما عند الله من العقوبة، ما طَمِع بِجَنَّتِهِ أحدٌ، ولو يَعلمُ الكافرُ ما عند الله من الرَّحمة، ما قَنَطَ من جَنَّتِهِ أحدٌ». [صحيح.] - [رواه مسلم.]"