A person who is concerned for himself is like a servant whose master has dispatched him on a mission. The master had sent him to some land that the master owns in order to procure some cloth there for him. When the servant arrives in that place, he begins to say to himself, "Where will I reside? Whom will I marry?" He gets preoccupied with these questions, expanding all his energy on anxiety about these concerns, until he is delinquent in executing the commands for which his master had sent him. When his master calls on him, his reward from the master will be that the master cuts him off and separates himself from the servant, since he was totally preoccupied by his own affairs rather than observing the prerogatives and rights of his master.
So it is with you, my fellow believer. The True One has dispatched you to this world and commanded you to serve in it faithfully, and has undertaken to support and sustain your existence contingent on your service. If you become engrossed in worrying about your own concerns for yourself and neglect the rights held over you by your master, then you have turned aside from the path of right guidance and slid down the low road to ruin.
Ibn 'Ata' Allah al Iskandari [ d.1309]
The Book of Illumination
Kitab al-Tanwir fi Isqat al-Tadbir