أُوْلَـيِكَ الَّذِينَ خَسِرُواْ أَنفُسَهُمْ

They are those who have lost their own selves,

They lost themselves, meaning that they be made to enter a blazing Fire, where they will be punished, and its torment will not be lifted from them for even the blinking of an eye.

This is as Allah said,

كُلَّمَا خَبَتْ زِدْنَاهُمْ سَعِيرًا

Whenever it abates, We shall increase for them the fierceness of the Fire. (17:97)

Concerning the statement,
 
وَضَلَّ عَنْهُم

and eluded them,

meaning that it has left them.
 
مَّا كَانُواْ يَفْتَرُونَ
 
 

that which they invented.

besides Allah, such as rivals and idols. Yet, these things did not avail them in the slightest. In fact, these things actually caused them great harm.

This is as Allah says,

وَإِذَا حُشِرَ النَّاسُ كَانُواْ لَهُمْ أَعْدَاءً وَكَانُواْ بِعِبَادَتِهِمْ كَـفِرِينَ

And when mankind are gathered, they will become their enemies and will deny their worshipping. (46:6) 

Allah says,

إِذْ تَبَرَّأَ الَّذِينَ اتُّبِعُواْ مِنَ الَّذِينَ اتَّبَعُواْ وَرَأَوُاْ الْعَذَابَ وَتَقَطَّعَتْ بِهِمُ الاٌّسْبَابُ

When those who were followed disown those who followed (them), and they see the torment, then all their relations will be cut off from them. (2:166)

Likewise, there are many other verses that prove this loss of theirs and their destruction.

For this reason Allah says,

لَا جَرَمَ أَنَّهُمْ فِي الااخِرَةِ هُمُ الَاخْسَرُونَ