Do not be sad. If you are poor, then someone else is immersed in debt. If you do not own your own means of transportation, then someone else has been deprived of his legs. If you have reason to complain concerning the pains of sickness, then someone else has been bedridden for years. And if you have lost a child, then someone else has lost many children, for instance, in a single car accident.
Do not be sad. You are a Muslim who believes in Allah, His Messengers, His angels, the Hereafter, and Preordainment --- both the good and the bad of it. While you are blessed with this faith, which is the greatest of blessings, others disbelieve in Allah, discredit the Messengers, differ among themselves concerning the Book, deny the Hereafter, and deviate in their understanding of Divine Preordainment.
Do not be sad, because if you are, you disturb your soul and heart, and you prevent yourself from sleeping. One of the Arab poets said:
"How often is the young man overcome with despair when afflicted, and with Allah is the way out, The situation becomes unbearable, and when its rope tightens, it snaps, and throughout, he never thought that he would be saved."