Is the fear of Allah's decree and the loss of trust in Him after repeated severe afflictions, such as sorcery, illness, and surgeries, a natural thing, and what is its cause?

This world is a place of trial and test, and Paradise is the abode of happiness. If anyone were to be exempt from trials, it would be the Prophets. Indeed, Muhammad, peace be upon him, lived a life full of trials, but he persevered and knew that "the greatest reward comes with the greatest trial. When Allah loves a people, He tests them. Whoever is pleased (with Allah's decree) will have pleasure, and whoever is displeased will have displeasure."

Patience in the face of affliction and seeking reward from Allah lead to good outcomes. Distress may be due to weak faith, for a believer content with Allah's decree finds tranquility and praises Allah that the affliction is not in their religion.

Trust in Allah and have a good opinion of Him, for all of Allah's decrees are good, even if they appear painful. "No fatigue, nor disease, nor sorrow, nor sadness, nor hurt, nor distress befalls a Muslim, even if it were a prick of a thorn, but Allah expiates some of his sins thereby," and "Wondrous is the affair of the believer, for there is good in every matter of his... If he is granted ease, he is thankful and that is good for him. And if he is afflicted with a hardship, he perseveres and that is good for him."

To increase your faith: listen to the Quran and reflect on it, regularly engage in the remembrance of Allah, attend gatherings of knowledge and goodness, return to your calling and do not let Satan prevent you from doing good. There is a cure for magic.