Sincerity cannot coexist in a heart that contains the love of praise and commendation and the yearning to possess that which is owned by the people save in the manner that fire and water or a lizard and fish may coexist. If your soul directs you to seek sincerity then first turn your attention towards your yearning and slaughter it with the knife of renunciation. Then turn your attention towards praise and commendation and forsake it with the asceticism of those who loved the world for the sake of the Hereafter. When your slaughtering of your yearning and the renunciation of praise and commendation becomes firm then attaining sincerity will become easy for you.
Ibn Al Qayyim (ra7imahullah)