The surah lightened its own command

The shortest statement of the same principle, and it sits in another surah entirely, worth having on its own. The lightening is a response to what a person is, not a reward for what they managed.

يُرِيدُ ٱللَّهُ أَن يُخَفِّفَ عَنكُمۡۚ وَخُلِقَ ٱلۡإِنسَٰنُ ضَعِيفࣰ ا

God wishes to lighten your burden; man was created weak

Qur’an 4:28

Surat al-Muzzammil opens here, addressing the Prophet enfolded in his cloak, peace be upon him. It is shown from its first verse because what matters is what the same surah does by its end.

يَٰٓأَيُّهَا ٱلۡمُزَّمِّلُ

You [Prophet], enfolded in your cloak

Qur’an 73:1

This is the command itself and it is demanding, which is why so many people have met the first half of this surah and stopped there.

قُمِ ٱلَّيۡلَ إِلَّا قَلِيلࣰ ا

Stay up throughout the night, all but a small part of it

Qur’an 73:2

The regimen is being specified in detail here, and that detail is what makes the lightening at the end of the same surah so striking.

نِّصۡفَهُۥٓ أَوِ ٱنقُصۡ مِنۡهُ قَلِيلًا

half, or a little less

Qur’an 73:3

The last of the clauses that set the regimen out, and it is the thing the same surah then lightens by name.

أَوۡ زِدۡ عَلَيۡهِ وَرَتِّلِ ٱلۡقُرۡءَانَ تَرۡتِيلًا

or a little more; recite the Quran slowly and distinctly

Qur’an 73:4

And here is the lightening, at the end of the same surah, with the ill, those travelling and those working named among the reasons. If you believe the night vigil is a fixed standard you are failing, you have stopped reading before the end of the surah.

۞إِنَّ رَبَّكَ يَعۡلَمُ أَنَّكَ تَقُومُ أَدۡنَىٰ مِن ثُلُثَيِ ٱلَّيۡلِ وَنِصۡفَهُۥ وَثُلُثَهُۥ وَطَآئِفَةࣱ مِّنَ ٱلَّذِينَ مَعَكَۚ وَٱللَّهُ يُقَدِّرُ ٱلَّيۡلَ وَٱلنَّهَارَۚ عَلِمَ أَن لَّن تُحۡصُوهُ فَتَابَ عَلَيۡكُمۡۖ فَٱقۡرَءُواْ مَا تَيَسَّرَ مِنَ ٱلۡقُرۡءَانِۚ عَلِمَ أَن سَيَكُونُ مِنكُم مَّرۡضَىٰ وَءَاخَرُونَ يَضۡرِبُونَ فِي ٱلۡأَرۡضِ يَبۡتَغُونَ مِن فَضۡلِ ٱللَّهِ وَءَاخَرُونَ يُقَٰتِلُونَ فِي سَبِيلِ ٱللَّهِۖ فَٱقۡرَءُواْ مَا تَيَسَّرَ مِنۡهُۚ وَأَقِيمُواْ ٱلصَّلَوٰةَ وَءَاتُواْ ٱلزَّكَوٰةَ وَأَقۡرِضُواْ ٱللَّهَ قَرۡضًا حَسَنࣰ اۚ وَمَا تُقَدِّمُواْ لِأَنفُسِكُم مِّنۡ خَيۡرࣲ تَجِدُوهُ عِندَ ٱللَّهِ هُوَ خَيۡرࣰ ا وَأَعۡظَمَ أَجۡرࣰ اۚ وَٱسۡتَغۡفِرُواْ ٱللَّهَۖ إِنَّ ٱللَّهَ غَفُورࣱ رَّحِيمُۢ

[Prophet], your Lord is well aware that you sometimes spend nearly two-thirds of the night at prayer––sometimes half, sometimes a third––as do some of your followers. God determines the division of night and day. He knows that you will not be able to keep a measure of it and He has relented towards all of you, so recite as much of the Quran as is easy for you. He knows that some of you will be sick, some of you travelling through the land seeking God’s bounty, some of you fighting in God’s way: recite as much as is easy for you, keep up the prayer, pay the prescribed alms, and make God a good loan. Whatever good you store up for yourselves will be improved and increased for you. Ask God for His forgiveness, He is most forgiving, most merciful

Qur’an 73:20