Letter to the disciple, from Imam al-Ghazali

Giving advice is an easy thing, but the hardest part is accepting it and following it, for it tastes bitter to those who follow their passions because prohibitions are sweet to their hearts.

Righteousness with Allah is sacrificing one's own desires to comply with God's commands

As for the extravagant state and the mystical ecstasies, you must not delude yourself, for the conduct in this path requires spiritual combat and intense effort: thus, it is by breaking the desires of the carnal soul and by annihilating his caprices with the sword of the spiritual exercises that one advances, and not with futilities and vain chimeras.