You suffer because of your sins
What comes to you of good is from Allah, but what comes to you of evil, [O man], is from yourself. And We have sent you, [O Muhammad], to the people as a messenger, and sufficient is Allah as Witness.
Qur'ān 4:79
Ibn Kathīr (paraphrase) writes:
ثم قال تعالى - مخاطبا - للرسول [ صلى الله عليه وسلم ] والمراد جنس الإنسان ليحصل الجواب : ( ما أصابك من حسنة فمن الله ) أي : من فضل الله ومنه ولطفه ورحمته ( وما أصابك من سيئة فمن نفسك ) أي : فمن قبلك ، ومن عملك أنت كما قال تعالى : ( وما أصابكم من مصيبة فبما كسبت أيديكم ويعفو عن كثير ) [ الشورى : 30 ] .
The good which comes to you is from the Mercy and Bounty of Allāh.
The evil which affects you is a result of your deeds and sins.
Allāh says:
And whatever strikes you of disaster - it is for what your hands have earned; but He pardons much.
Qur'ān 42:30
Narrated `Aisha (the wife of the Prophet) Allah's Messenger (sallallaahu alayhi wa sallam) said:
"No calamity befalls a Muslim but that Allah expiates some of his sins because of it, even though it were the prick he receives from a thorn."
Sahīh al-Bukhāri Hadīth No. 5640
Imām al-Tabari (paraphrase) writes:
يقول تعالى ذكره: وما يصيبكم أيها الناس من مصيبة في الدنيا في أنفسكم وأهليكم وأموالكم ( فَبِمَا كَسَبَتْ أَيْدِيكُمْ ) يقول: فإنما يصيبكم ذلك عقوبة من الله لكم بما اجترمتم من الآثام فيما بينكم وبين ربكم ويعفو لكم ربكم عن كثير من إجرامكم, فلا يعاقبكم بها
Allāh says: O mankind what befalls you of distress in this world in yourselves, your family, and your wealth is a punishment from Allāh because of the sins you did, and Allāh forgives many of your sins and does not punish you for them.
Imām al-Tabari goes on to write:
يعجل للمؤمنين عقوبتهم بذنوبهم ولا يؤاخذون بها في الآخرة
The punishment for the believer (because of his sins) is hastened (in this world), and he is, then, not punished for his sins in the next world.
Anas narrated that the Messenger of Allah (sallallaahu alayhi wa sallam) said:
"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."
And with this (same) chain, (it was reported) from the Prophet (sallallaahu alayhi wa sallam) who said: "Indeed greater reward comes with greater trial. And indeed, when Allah loves a people He subjects them to trials, so whoever is content, then for him is pleasure, and whoever is discontent, then for him is wrath."
Jāmi' al-Tirmidhi Hadīth No. 2396
Reference (s):
Tafsīr al-Tabari
Tafsīr Ibn Kathīr