Life is a test whose success depends upon good deeds and piety. Often man forgets his ultimate purpose and spends his life pursuing the desires of the lower self (nafs). Following the nafs’ desires in any form is a type of idol worship. The devil is man’s outer enemy, and the nafs is his enemy within. REmember, an enemy within is always more dangerous than any enemy on the outside.
Sh. Zulfiqar Ahmad Naqshbandi Mujaddidi in Wisdom for the Seeker letter 5