Du'a for good character

اللَّهُمَّ إِنِّي أَعُوذُ بِكَ مِنْ مُنْكَرَاتِ الْأَخْلَاقِ وَالْأَعْمَالِ وَالْأَهْوَاءِ

Allahumma inni a'udhu bika min munkaratil-akhlaqi wal-a'mali wal-ahwa'

O Allah, I seek refuge in You from reprehensible manners, deeds, and whims.

Jāmiʿ al-Tirmidhī 3591