Why did God destine for me a job that caused me psychological harm and weakened me in my religious devotion and acts of worship, even though I sought His guidance through Istikhara and expected good from it?

Whoever seeks guidance from Allah Almighty and acts upon what the Prophet, peace and blessings be upon him, guided to, let him be assured of good, for what he is experiencing is not the end of the journey. He must be patient with what Allah has decreed for him and content with what Allah has allotted him, so that he may be the happiest of people. Indeed, the affair of the believer is entirely good: if prosperity befalls him, he is grateful, and that is good for him; and if adversity befalls him, he is patient, and that is good for him. The question: "Why did Allah decree this for me?" is not befitting for a Muslim, because Allah is not questioned about what He does, while they will be questioned. The servant must be content with Allah's decree and predestination, and know that there is good in it for him, sooner or later.