negligence of religious duties

أَن تَقُولَ نَفْسٌ يَـٰحَسْرَتَىٰ عَلَىٰ مَا فَرَّطتُ فِى جَنۢبِ ٱللَّهِ وَإِن كُنتُ لَمِنَ ٱلسَّـٰخِرِينَ

Lest a soul should say, "Oh, [how great is] my regret over what I neglected in regard to Allāh and that I was among the mockers."