Imam Sadjad (A.S) said: “How poor son of Adam is! Every day, he is inflicted with three misfortunes. Nevertheless, he does learn lessons from any. Had he learnt a lesson, all the misfortunes of this worldly life would have been easy in his sight. The first misfortune is that the day which comes upon him decreases his age. If a decrease occurs to his wealth, he will become so depressed, while he can cover the decrease of wealth, but he cannot regain the decrease of his age. The second misfortune is that he takes the sustenance that is decided for him completely. If he gets it in a legal way, he will be interrogated about it, and if he gets it in an illegal way, he will be punished for it. The third misfortune, which is the most calamitous, is that each day that ends takes him a stage closer to the Hereafter, while he does not know whether his fate will be Paradise or Hell." (1)
“On the day of his birth, man is the oldest."
Imam Baqir (A.S) said: “Let not people deceive you in matters regarding yourself, because you exclusively will encounter your own matters. Do not spend your days with gossips and nonsense, for there are the angels who accompany you and record all your deeds. Do righteous deeds, because I have not seen anything better in result and remedying than a new good deed after an old sin." (2)
Imam Sadiq (A.S) said: “Be tolerant in the acts of obedience to Allah and steadfast against the acts of disobedience to Him. This world is no more than an hour. You will not find the pleasures of what has passed away and you will not be able to recognize what is coming. Be patient in that hour and you will attain bliss." (3)
A wise man said: “Man is like a traveller who has to pass by six stations. He, however, has already passed by three: the first is the transition from nonexistence to his father’s loins and mother’s ribs. The second is the transition to the mother’s womb. The third is the transition from the mother’s womb to the world. The three stations that man has not passed by yet are the grave, the field of the Resurrection, and Hell or Paradise."
We are now living in the third station whose distance takes our lifetime. Hence, days of our ages are miles, hours are meters and breaths are steps. Some of us have only few miles, others have only few meters, and others have only few steps.

Notes:
1. This is because every single day that man lives in decreases his age. This nice maxim was not said by anyone before Imam as-Sejjad (A.S). Quoted from al-Mufid’s Alikhtissas.
2. Quoted from al-Wafi; part 3 page 168 (as quoted from al-Kafi).
3. Quoted from al-Wafi; part 3 page 168 (as quoted from al-Kafi).