A person’s life in this world is not stable. One passes through alternating periods of happiness and dismay, strength and weakness, wealth and poverty, health and sickness, etc.

A true believer is one who maintains a clear level of faith throughout the worldly fluctuations. He continues to remember Allah and ascribe the bounties to Him, and he turns to Him in submission, asking for relief from his affliction.

This is described by the Messenger of Allah ﷺ, who said,
‏عجبا لأمر المؤمن إن أمره كله له خير، وليس ذلك لأحد إلا للمؤمن ‏:‏ إن أصابته سراء شكر فكان خيراً له، وإن أصابته ضراء صبر فكان خيراً له‏‏
“Indeed amazing are the affairs of a believer! They are all for his benefit. If he is granted ease of living he is thankful and this is best for him. And if he is afflicted with a hardship, he perseveres; and this is best for him.” (Muslim)

And Allah said,
وَلَنَبْلُوَنَّكُم بِشَىْءٍ مِّنَ ٱلْخَوْفِ وَٱلْجُوعِ وَنَقْصٍ مِّنَ ٱلْأَمْوَٰلِ وَٱلْأَنفُسِ وَٱلثَّمَرَٰتِ ۗ وَبَشِّرِ ٱلصَّـٰبِرِينَ
ٱلَّذِينَ إِذَآ أَصَـٰبَتْهُم مُّصِيبَةٌ قَالُوٓا۟ إِنَّا لِلَّهِ وَإِنَّآ إِلَيْهِ رَٰجِعُونَ
أُو۟لَـٰٓئِكَ عَلَيْهِمْ صَلَوَٰتٌ مِّن رَّبِّهِمْ وَرَحْمَةٌ ۖ وَأُو۟لَـٰٓئِكَ هُمُ ٱلْمُهْتَدُونَ
Certainly, We shall test you with fear, hunger, loss of wealth, lives and fruits; but give glad tidings to the patient—those who, when afflicted with calamity say, “Truly to Allah we belong, and truly to Him shall we return.” It is those who will be awarded blessings and mercy from their Lord; and it is those who are the guided ones. [Al-Baqarah 2: 155–157]

Thus, a believer shows gratitude and thankfulness for all the wonderful blessings that Allah grants him. And he displays patience and submission during sickness and hardships, hunger, or other afflictions.

Allah has decreed that, in this life, hardships and disasters strike both believers and non-believers. For a non-believer, they are inconveniences that hinder him from proceeding with his normal involvement in the worldly life.
For a believer, on the other hand, they are instances of test and remembrance, tests that promise great rewards, and indications of atonement and expiation of sins.
Regardless of how little is the harm that strikes a believer, it carries with it good news of forgiveness and elevated rank in Paradise. The Righteous Predecessors used to be pleased when a hardship afflicted them, seeing it as a token of Allah’s forgiveness and benevolence.

Let`s take a look at the rewards which a believer gets for the difficulties he had to undergo.

Expiations of Sins
Abu Hurairah (may Allah be pleased with him) reported that the Prophet ﷺ said:
مَا يَزَالُ الْبَلاَءُ بِالْمُؤْمِنِ وَالْمُؤْمِنَةِ فِي نَفْسِهِ وَوَلَدِهِ وَمَالِهِ حَتَّى يَلْقَى اللَّهَ وَمَا عَلَيْهِ خَطِيئَةٌ
“Trials will not cease afflicting the believing man and the believing woman in their self, children, and wealth, until they meet Allah without having any sin.” [At-Tirmidhi 2399]

Sign of Allah’s Love
Abu Hurairah RA reported that the Prophet ﷺ said:
‏ مَنْ يُرِدِ اللَّهُ بِهِ خَيْرًا يُصِبْ مِنْهُ ‏
“Whenever Allah wills good for a person, He subjects him to adversity” [Al-Bukhari and others]

Sign of Faith
Abu Hurairah RA and Ka`b ibn Malik RA reported that the Prophet ﷺ said:
مَثَلُ الْمُؤْمِنِ كَمَثَلِ الْخَامَةِ مِنَ الزَّرْعِ مِنْ حَيْثُ أَتَتْهَا الرِّيحُ كَفَأَتْهَا، فَإِذَا اعْتَدَلَتْ تَكَفَّأُ بِالْبَلاَءِ، وَالْفَاجِرُ كَالأَرْزَةِ صَمَّاءَ مُعْتَدِلَةً حَتَّى يَقْصِمَهَا اللَّهُ إِذَا شَاءَ
“The example of a believer is that of a fresh tender plant; from whatever direction the wind comes, it bends it, but when the wind becomes quiet, it becomes straight again. Similarly, a believer is afflicted with calamities (but he remains patient till Allah removes his difficulties.) And an impious wicked person is like a pine tree which keeps hard and straight till Allah cuts (breaks) it down when He wishes.” [Al-Bukhari 5644]

Sign of Righteousness
The prophets AS and righteous people are afflicted the most, and their rewards are the highest.
It was narrated from Mus’ab bin Sa’d that his father, Sa’d bin Abi Waqqas, RA said:
عَنْ أَبِيهِ، سَعْدِ بْنِ أَبِي وَقَّاصٍ قَالَ قُلْتُ يَا رَسُولَ اللَّهِ أَىُّ النَّاسِ أَشَدُّ بَلاَءً قَالَ ‏ “‏ الأَنْبِيَاءُ ثُمَّ الأَمْثَلُ فَالأَمْثَلُ يُبْتَلَى الْعَبْدُ عَلَى حَسَبِ دِينِهِ فَإِنْ كَانَ فِي دِينِهِ صُلْبًا اشْتَدَّ بَلاَؤُهُ وَإِنْ كَانَ فِي دِينِهِ رِقَّةٌ ابْتُلِيَ عَلَى حَسَبِ دِينِهِ فَمَا يَبْرَحُ الْبَلاَءُ بِالْعَبْدِ حَتَّى يَتْرُكَهُ يَمْشِي عَلَى الأَرْضِ وَمَا عَلَيْهِ مِنْ خَطِيئَةٍ ‏”
“I said: ‘O Messenger of Allah, which people are most severely tested?’ He said: ‘The Prophets, then the next best and the next best. A person is tested according to his religious commitment. If he is steadfast in his religious commitment, he will be tested more severely, and if he is frail in his religious commitment, his test will be according to his commitment. Trials will continue to afflict a person until they leave him walking on the earth with no sin on him.’” (Hasan) [Sunan Ibn Majah 4023]

Early Purification
Anas RA reported that the Prophet ﷺ said:
إِذَا أَرَادَ اللَّهُ بِعَبْدِهِ الْخَيْرَ عَجَّلَ لَهُ الْعُقُوبَةَ فِي الدُّنْيَا وَإِذَا أَرَادَ اللَّهُ بِعَبْدِهِ الشَّرَّ أَمْسَكَ عَنْهُ بِذَنْبِهِ حَتَّى يُوَفَّى بِهِ يَوْمَ الْقِيَامَةِ
“When Allah wants good for his slave, He hastens his punishment in the world. And when He wants bad for His slave, He withholds his sins from him until he appears before Him on the Day of Judgement.” (Hasan) [At-Tirmidhi 2396]