He will wish that he performed good acts of obedience in his worldly life for the sake of this afterlife, which is the real life.

يَا لَيْتَنِي (Oh, I wish): As if he is calling and wishing. To wish is to hope something lovely, no way to have it. Allah (swt) says:

 {وَإِنَّ الدَّارَ الْآخِرَةَ لَهِيَ الْحَيَوَانُ ۚ لَوْ كَانُوا يَعْلَمُونَ}

(And indeed, the home of the Hereafter – that is the [eternal] life, if only they knew.) (Al-Ankaboot: 64)