Imam Khomeini explains the matter in his famous book "Combat with the self" as following:
If you are dominated by love of the world and love of the self, and if this prevents you from perceiving truths and realities, and prevents you from performing deed purely for God, and if you are kept from enjoining the truth and enjoining patience, and you are thereby obstructed from the way to guidance, then you will be lost.
You will be lost in this world and in the next, for you will have given up your youth and will be prohibited from the blessings of heaven and otherworldly advantages, and also lack this world, Imam further explained.
If others have no way to heaven, and if the doors to divine mercy are closed to them, if they are to abide eternally in the fire of hell, at least they will have had the world, they will have enjoyed worldly advantages, but you…
Beware, lest love of the world and love of the self gradually increase within you, to the point that Satan is able to take away your faith.
It is said that all of the efforts of Satan are for the sake of robbing faith.
All of his efforts and labors, night and day, are for the sake of taking away the faith of men.
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