The lower soul (nafs) is always engaged in inspiring your imagination to pursue evil acts or thoughts, every moment striving to cast you down into the abyss of pride, hypocrisy, and egotism. Each moment thus demands that you overcome and repulse such evil thoughts and false conceptions, constantly regaining your faith afresh and reaffirming your belief, and never imagining yourself safe from the lower soul's deceit even for a second. Every fantasy which oppresses you - driving you to infidelity and being veiled (kufr u ihtijab), casting you down from your sublime station into the deepest pits of passions and carnal nature - must be met and opposed with fresh faith, lest the citadel of your religion to be destroyed by the lasso of lust and the sabre of wrath.- Lahiji in Mafatih
From: The Wisdom of Sufism
O son, you should not be sad if you lost a friend who has the tendency to drag you down with his lower nafs. You might feel sad at first at losing such a friend, but know that the part of you who is sad for the loss is actually your lower soul (nafs) because it could no longer fulfill its fancies. So keep fighting and be strong. When you leave anything munkar (forbidden) for the sake of Allah, He will reward you with something better and far more worthwhile. Bi-iznillah.