Nafs in the Quran is translated with terms like “yourself” and “soul”. 

“And do thou (O reader!) Bring thy Lord to remembrance in thy (very) soul” in another translation “And remember your Lord within yourself” (7:205)

“And fear a Day when no soul will suffice for another soul at all” (2:48)  

“There is no soul but has a protector over it” (86:4) 

In the verse: “And I do not acquit myself. Indeed, the soul is a persistent enjoiner of evil, except those upon which my Lord has mercy. Indeed, my Lord is Forgiving and Merciful” (12:53) the soul is described with a specific characteristic, or at least a part of the soul is described with the ability to do evil, it might even prone to evil. The soul is described with three different qualities: 

“1) The despotic soul which leads one to commit evil and vicious acts. If it is not controlled by faith and reason, it results in man’s sudden fall.
2) The reproaching soul. This self or ego is active when a guilty person blames and scolds himself. In this case, he tends to seek repentance and is apologetic for the sin or crime which he has committed.
3) The peaceful soul which is found in only the prophets, and those truly trained by them. Once they find themselves surrounded by unbridled passion and ignorance, they seek the help of Allah to be extricated from it. They owe everything to Allah who loves them very much.” (From: An enlightening commentary into the light of the Holy Qur’an: https://www.al-islam.org/enlightening-commentary-light-holy-quran-vol-7/...)

In the verse: “By the Soul, and the proportion and order given to it; And its enlightenment as to its wrong and its right; He has succeeded who purifies it” (91:7-9), we are taught that God taught man how to discriminate between right and wrong (https://www.al-islam.org/enlightening-commentary-light-holy-quran-vol-20...). Further explained in the commentary of the Holy Qur’an: 

“The purpose of using the term /taqwa/ based on /wiqayah/ with the meaning of 'protection', is that Man protects himself from sin, crime, corruption and vice.
It is necessary to note that verse 8 does not mean, as some have considered, that Allah put the means of committing / fujur/ and /taqwa / inside the soul of Man; the very means which cause him to do wrong actions and break the curtains of piety, or the means and ways that push him towards piety and good actions.
They have thought of the verse as an evidence for the existence of some contrariety in the entity of Man.
It says that Allah inspired him and taught him these two facts.” (https://www.al-islam.org/enlightening-commentary-light-holy-quran-vol-20...). 

The soul is inspired by God, as it is explained in the commentary: 
“the soul is inspired by Allah; its Almighty and All-wise Author, with the consciousness and the faculty of discretion to distinguish between piety and impiety, right conduct and the wrong ways in life, by the means of his 'wisdom' and 'primordial nature'.
This is why some commentators believe that this verse, in fact, refers to the proposition of the idea of 'rational goodness and rational badness' and that Allah has gifted Man with the ability to distinguish between them.
It is noteworthy that Allah has given Man many blessings, but, among all of them the Qur'an emphasizes, here on the inspiration of understanding 'piety' and 'impiety' and the recognition of right and wrong, because this is the most important factor in the destiny of Man.
Finally, after these numerous important oaths, attention is paid to the result of them and says:
"Indeed he succeeds who purifies it,"
The term /zakkaha/ is based on /tazkiyah/ which originally means 'to grow’; and /zakat / basically means 'growth'.” (https://www.al-islam.org/enlightening-commentary-light-holy-quran-vol-20...). 

The purpose of the creation of man (the soul) is for the creations to find nearness to God. Obtaining nearness to God is the only true happiness (bliss) one may experience. The only happiness that lasts. The soul is in constant longing for happiness, and searches for it. The soul has to be purified in order to see and understand the true goal of creation, otherwise it will search for temporary happiness in worldly or harmful affairs. God has already inspired the soul to do good, and to reach it’s purpose the soul was gifted with tools and merits for this aim.  “Such as; a wakeful conscience and a sense of understanding piety and impiety for paving the way to felicity.” (https://www.al-islam.org/enlightening-commentary-light-holy-quran-vol-20...). 

For further readings, go to the “Shi’ite Creed” by Shaykh Saduq pg. 32 (https://www.al-islam.org/printpdf/book/export/html/12317)