Just like your heart, mind, and soul; the nafs (self) is a part of you. In Ustadh Bediuzzaman’s words “Your nafs is the source of pleasure and benefit” [Twenty Fourth Word, Fifth Branch, First Fruit]. It is due to your nafs that you desire such things as food, marriage, wealth and so on. Similarly, it is your nafs that urges you to commit acts that are wrong or sinful such as lying, eating too much, cheating, and anything else that you take pleasure or benefit from. Note that sometimes the word nafs is used to mean “you” as a whole instead of being the part of you which causes you to desires things. So it is essential to look at the context. 

Basically, it would be much easier to control ourselves if we could get rid of our nafs. Thus, it is a tradition in many Sufi orders to kill one’s nafs in order to move closer to God. This is usually accomplished by limiting necessities such as food or sleep to the bare minimum and avoiding foods or things which one desires. Over time, one’s desires begin to fade. One reaches a point where they no longer feel pleasure from things that others do. The nafs dies.   

While killing your nafs will certainly protect you from sin and bring you closer to God, training your nafs so that it desires what is good is superior to killing it as seen in the following quote by Imam Rabbani (رحمه الله).  

He states,

People have understood riyadat [i.e. staying away from worldly desires] to mean staying hungry and fasting voluntary fasts. However, to pay attention to eating as much as our religion has commanded is more difficult and beneficial than fasting voluntary fasts for thousands of years. It is an intense riyadat and much superior than other forms of riyadats if tasty sweet foods were to be placed before someone and if he ate what our religion commands, leaving the rest despite having an appetite and wanting to eat them all. [Manaqib Ahmadiyya]

Essentially, a nafs that is properly trained allows one to better thank God for the favors he bestows upon us. How so? We will give an example about food but the same applies to anything of worldly nature.

Suppose we have two people X and Y seeking God through the path of killing the nafs and training the nafs, respectively. Suppose person X forbids himself from eating anything he finds tasty for many years. Over time, he reaches a point where he loses his appetite for these foods (and similarly with other worldly things). He no longer feels pleasure or joy from this world and turns completely to God.

Now unlike person X, suppose person Y trains his nafs as apposed to killing it. That is, instead of letting his desires fade and disappear, he changes his perspective so that everything reminds him of God. For instance, when he eats something delicious, he thinks of how Merciful and Generous his Creator is to provide him with such tasty food. The joy he feels from eating motivates him to reflect upon the food’s Creator. Essentially, he can appreciate the favors of God better than person X due to his nafs which is still alive but properly trained.

Note that this does not mean it is ok to indulge in food or other worldly pleasure. It simply means that the best way is the middle way: to eat when necessary and refrain from what is excessive. Also, it is not necessary to limit the variety of food in order to move closer to Allah (سبحانه و تعالى).

Finally, this is one reason why the companions of the prophet (عليه الصلاة و السلام) are superior to the rest of the awliya’ (saints). Because they (رضي الله عنهم) trained their nafs as opposed to killing it and thus were better able to thank God and comprehend His names. Regarding this matter, Ustadh Bediuzzaman states,

While the people of walayat (saints) succeed in dissolving the nafs – they kill the evil commanding nafs (nafs ul ammara) – they still cannot reach the companions of the prophet (pbuh). Because the nafs of the companions were cleansed and purified so that, with the abundant tools in the nature of nafs, they are greater recipients of the varieties of worship and segments of thanks and glorification (of God).  After dissolving the nafs, the worship of awliya’ (saints) manifests simplicity. [Twenty Seventh Word, Addendum to the Twenty Seventh Word, Third Reason, Second Aspect]

RELAVANET PASSAGE FROM THE EIGHTH WORD

Also, that unfortunate one hastens his torment by eating the apparently delicious [but] spiritually poisonous fruits. Because those fruits are samples, there is permission to taste them so that one asks for their originals and becomes a customer. But there is no permission to swallow them like an animal. And this fortunate one, on the other hand, tastes [them], understands the matter, postpones eating them, and feels joy in waiting.