Hisnul Muslim 59

After the final tashahhud and before salam

اللَّهُمَّ أَعِنِّي عَلَى ذِكْرِكَ وَشُكْرِكَ، وَحُسْنِ عِبَادَتِكَ

Allaahumma 'a'innee 'alaa thikrika, wa shukrika, wahusni 'ibaadatika.

O Allah, help me to remember You, to give You thanks, and to perform Your worship in the best manner.