Don't be Sad
Prepare for bad times by being Thankful when all is well
Supplicate often in times of comfort, peace, and well-being. Among the characteristics of the believer is that he is thankful and resolute: he sharpens the arrow before releasing it from the bow, and he turns to Allah before he is afflicted. The opposites of the believer in this regard are both the vile disbeliever and the injudicious Muslim.
(And when some hurt touches man, he cries to his Lord [Allah Alone], turning to Him: in repentance, but when He bestows a favor upon him from Himself he forgets that for which he cried for before, and he sets up rivals to Allah…) (Qur'an 39: 8)
Therefore if we truly want to be saved, we must remain steadfast in supplicating and praising Allah. The purpose of supplicating to Allah during times of ease, as has been mentioned by Imam Al- Haleemee, is to praise Allah, to thank Him, and to recognize His many favors; and at the same time, to ask for guidance and help. It is also important to seek forgiveness for your shortcomings: no matter how hard you try, you cannot completely fulfill the rights that Allah has upon you. When one remains heedless of those rights at a time when he has no worries or when he feels secure, he falls under the category of those mentioned in the verse:
(And when they embark on a ship, they invoke Allah, making their Faith pure for Him only but when He brings them safely to land, behold, they give a share of their worship to others.)
(Qur'an 29: 65)