Hazrat Moulana Ashraf Ali Thanwi (rahmatullahi ‘alaih) once mentioned:

Acquiring sustenance is not based on one’s intelligence, but rather it is based entirely on the grace of Allah Ta‘ala. There are thousands of people in the world who are not intelligent, yet they are blessed with much more sustenance than those who are intelligent. Allah Ta‘ala says in the Quraan Majeed:

اَللّٰهُ یَبْسُطُ الرِّزْقَ لِمَنْ یَّشَاءُ وَیَقْدِرُ

Allah Ta‘ala expands (increases) sustenance for whomsoever He wishes, and restricts (sustenance for whomsoever He wishes).

From this aayah, we understand that sustenance is the sole prerogative of Allah Ta‘ala. He deals with His servants in the manner He wishes. Therefore, if Allah Ta‘ala blesses one with sustenance, he should remain grateful to Allah Ta‘ala at all times for this great favour and never show any ingratitude. (Malfoozaat Hakeemul Ummat 5/261)

Source: Ihyaauddeen.co.za