Your youth will definitely leave you, and if you do not remain within the sphere of the licit, it will be lost, and rather than its pleasures, it will bring you calamities and suffering in this world, in the grave, and in the Hereafter. But if, with Islamic training, you spend the bounty of your youth as thanks honorably, in uprightness and obedience, it will in effect remain perpetually and-will be the cause of gaining eternal youth.
As for life, if it is without belief, or because of rebelliousness belief is ineffective, it will produce pains, sorrows and grief far exceeding the superficial, fleeting enjoyment and pleasure it brings. Because, since, contrary to the animals, man possesses a mind and he thinks, he is connected to both the pre- sent time, and to the past and the future.
He can obtain both pain and pleasure from them. Whereas, since the animals do not think, the sorrows arising from the past and the fears and anxieties arising from the future do not spoil their pleasure of the present. And especially if the pleasure is illicit; then it is like an altogether poisonous honey.
from: The Risale-i Nur Collection