One way to understand a word or concept is to comprehend it's opposite meaning. For example, if we'd like to understand what is light, we need to understand what darkness is. And if we desire to comprehend the meaning of heat, then we need to experience what cold is. Likewise, we can better understand the significance of Ne’mat by understanding what Neqmat / calamity is.
By definition, Neqmat means calamity, indignation, retaliation, or misfortune. Neqmat could affect us as a result of our unjust actions to ourselves or to others and the presence of Neqmat is equivalent to the absence of Ne’mat. Hence, we beseech Allah (SWT) at the end of Dua Kumail and call out to him
"يا سابغ النِعَم يا دافع النِقَم...
"You who perfects all bounties and who wards off all misfortunes!
We acknowledge that Allah (SWT) is the one who blesses us with bounties and He (SWT) is also capable of preventing calamities from reaching us. In the beginning of this beautiful supplication, we seek the forgiveness of Allah (SWT) from different types of sins. Among the categories of sins that are highlighted are the sins that change or reverse the Ne'am (bounties). So we implore our Lord and pray,
"اللهم إغفر لي الذنوب التي تُغيِّر النِعَم"
Oh Allah! Forgive me those sins that change divine blessings.
Committing certain sins alter Allah's blessings for human being and replaces them with calamities and adversities. As cited in the Commentary of Kumail Supplication according to Imam Al Sajjad (AS), one of these sins is being ungrateful and unthankful. True happiness is to enjoy bounties without calamities and the reversal of divine favours into disfavours is in essence the existence of Neqmat (calamity).
It's important to note that even though a Neqmat which Allah (SWT) is capable of bringing forth has no limit, the mercy which He (SWT) possesses is enough to drown the most severe types of Neqmat, as expressed in the prayer recited on Saturdays,
"واتسعت رحمتك في شدة نِقمتك واشتدت نقمتك في سعة رحمتك"
Your mercy is widespread even in the most toughest of Your calamities and Your calamities is severe in the presence of your endless mercy.
It is not the course of the Creator to change or transform the Ne'am (bounties) nor to hasten in bringing about the Neqam (calamities), as we call out Him in the Friday supplication in Saheefa Al Kamela by Imam Zainul Abideen (AS)
"يا من لا يُغيِر النعمة ولا يُبادر بالنقمة"
Oh He who changes not favours and rushes not to vengeance!
However, if the bounties we enjoy changes into Neqmat, it is due to our own actions and faults and that's why we pray in Dua Kumail to forgive those sins which changes the bounties.