Ibn al-Jawzī authored the following as an advice to his son, Abu’l-Qasim Badr al-Dīn ‘Alī al-Nasikh.1
You should know, my son, may Allāh guide you to what is right, that man has been distinguished by intellect only so that he would act according to it. Bring it to the fore, use it in contemplation and spend time alone with yourself. You will conclude that you are a created being who has responsibilities and obligations and that the two angels are counting your every word and glance. Every breath is a step closer to death. The time we spend in this world is short, the time we are held in our graves is long, and the punishment for following our base desires is calamitous.
Where is the delight of yesterday? It has departed leaving only regret in its wake. Where is the soul’s desire? How many has it brought low, how many has it caused to slip and falter? People have only attained happiness by going against their lusts and desires. People have only become wretched by giving preference to the life of this world. Learn from the lives of kings and ascetics: where is the delights of the kings and where is the weariness of the ascetics? The only thing left is the abundant reward and beautiful mention for the pious, and the malicious words and calamitous punishment for the disobedient. It is as if those who starved never starved and those who ate to their fill never did so. Laziness in virtuous deeds is an evil companion indeed, and love of comfort causes regret greater than any enjoyment. So take heed and tire yourself for your self.