Imam in his theological works has undertaken very useful discussions in this regard as following:
Maybe on account of the same mistrust in others, my acts will lead me to a miserable life in the Hereafter.
Our great master, the accomplished ‘arif, Shahabadi- r’uhi fidah- used to say, ‘Do not look down on even a kafir (non-believer) in your heart. It is possible that the divine light of his inner nature may lead him to faith and your rebuke and disdain may lead you towards a wretched life in the Hereafter.
Of course to practice al amr bi al-ma’r-uf wa al-nahy ‘an al-munhar (enjoining right conduct and forbidding bad behavior) is something different from the inner feeling of contempt.’
He would even say, ‘Never curse the unbelievers regarding whom it is not known that they will leave the world in the state of unbelief.
If they leave the world as rightly-guided servants of God, their spiritual rectitude may prove to be an obstruction in the way of your own spiritual advancement.’
In any case, beware that the Devil and the carnal self make man enter the preliminary stages of ‘ujb; and from this place, step by step, they slowly take him to higher stages of ‘ujb, and in this way, in degrees, they lead man to the wretched state in which he thinks that he is conferring a favor on God by having faith in Him and performing virtuous deeds.
This is the final stage of ‘ujb.
Know that ‘ujb in itself is a destructive and dangerous vice which spoils the faith and the deeds. In answer to the question by the narrator of the tradition about ‘ujb which corrupts human deeds, the Imam (A) mentions the ‘ujb in faith as one of its forms. We have read in the previous tradition that ‘ujb is considered by God Almighty to be something worse than sin, so much so that He makes a believer commit sin so that he may be saved from ‘ujb. The Holy Prophet (S) has reckoned ‘ujb as one of the greatest of spiritual dangers. In al-’Amali of Al-Shaykh al-Saduq, Imam ‘Ali (A) has been reported to have said:
The one into whose heart ‘ujb permeates is destined to be destroyed.
After death and in the purgatory (barzakh), the possessor of this evil experiences a dreadful loneliness, which is incomparable and unimaginable; in an advice given by the Prophet (S) before his death to Imam ‘Ali (A). he says:
No loneliness can be compared in dreadfulness to the one, which is the result of ‘ujb.