Why is this a loss? It is because, the human being is at work and is all the time increasing the capital he initially put in. If the capital itself decreases, the profit will also decrease, and he will lose the whole thing and the profit too. Likewise, the deeds of those who deny the meeting with Allah (swt) will go away like scattered dust, as Allah says:

 وَقَدِمْنَا إِلَى مَا عَمِلُوا مِنْ عَمَلٍ فَجَعَلْنَاهُ هَبَاء مَّنثُورًا

(Then We will turn to whatever (good) deeds they did, reducing them to scattered dust) (Al-Furqan: 23)

(… حَتَّىٰ إِذَا جَاءَتْهُمُ السَّاعَةُ بَغْتَةً… ) (…until when the Hour [of resurrection] comes upon them unexpectedly, …): (Until) is used as a bridge between two things. Here, it is used to mean ‘between this world and the hereafter. Surely, the Hour will come by surprise, and every person’s Hour will be his Day of Standing. During his death, his Hour will be even nearer to him than himself, whereas he does not know when it will happen. So, when it does come, his Day of Standing has occurred. Of course, the great Day of Standing will be when mankind will stand in front of the Lord of the universe. However, the end of the worldly term for a human being will be when he dies in this world, as a poet says:

We are moving towards the appointed term in every moment,

And our lives are brought to an end, which had consisted of stages,

I have never seen a reality like death, as if,

Whatever went beyond it of aspirations proved false,

How difficult is negligence during the early years,

How could it happen, when the head was full of white hair,

Leave the world with piety as your supply,

For your life is made up of days, which are but a few.

(… قَالُوا يَا حَسْرَتَنَا عَلَىٰ مَا فَرَّطْنَا فِيهَا… ) (…they will say, “Oh, [how great is] our regret over what we neglected concerning it,”…): On that day, they will regret, but this regret will not be of any benefit to them.

(  وَهُمْ يَحْمِلُونَ أَوْزَارَهُمْ عَلَىٰ ظُهُورِهِمْ ۚ أَلَا سَاءَ مَا يَزِرُونَ… ) (…while they bear their burdens on their backs. Unquestionably, evil is that which they bear): These sins will transform to weights and burdens on their backs. They do not only carry their sins, but the sins of those whom they were examples for in these acts, and who took them as examples in distancing from Allah (swt), His path, His blessings and His mercy.