سُبْحَانَ ٱللَّٰهِ
Holy Qur'an
Al-Qur'an
Kids Qur'an
Thus, the knowledge that whatever has happened had to happen - and could not have not happened - because, obviously, it had been willed by God in accordance with His unfathomable plan, ought to enable a true believer to react with conscious equanimity to whatever good or ill comes to him.
I.e., attributing their good fortune to their own merit or "luck".
In the external world, what people may consider misfortune or good fortune may both turn out to be illusory,-in Kipling's words, "both imposters just the same". The righteous man does not grumble if some one else has possessions, nor exult if he has them. He does not covet and he does not boast. If he has any advantages, he shares them with other people, as he considers them not due to his own merits, but as gifts of Allah.