Satan will use every Wound you Give Him
The mind is a battlefield, and some people are born into that battle with weaker walls than others. i don't think that is pleasant, fair or something that should be romanticized, but fairness has never been the measure of whether suffering exists. Some bodies become sick, some minds become sick, some people inherit wounds before they are old enough to understand what wounded them, and the enemy is not so courteous that he refuses to make use of damaged ground. satan sees weakness and wants possession of it. God sees weakness and demands that even this be brought under Him.
if satan desires despair, blasphemy, isolation, hatred of oneself, hatred of God, distrust, confusion and finally the destruction of a soul, why would he ignore a mind already suffering from things that can be bent toward exactly those ends ? he does not need to create the illness. A thief does not need to build the broken door in order to enter through it.
This is why i have become much less patient with the idea that every voice inside a person deserves to be heard simply because it comes from inside them, some thoughts deserve contradiction, some desires deserve starvation and some fears deserve disobedience. There are things the mind produces that should be taken to a doctor, things that should be taken to a therapist, things that should be taken to confession, and sometimes the same miserable thing needs to be carried to all three. Calling something a symptom does not consecrate it. Understanding where a thought came from does not require obeying where it wants to go.
The enemy would like the sick person to become devoted to the sickness. First you suffer from it, then you name yourself by it, then you arrange your life around it, then you defend everything it has taught you because separating the wound from yourself feels like being asked to cut away your own flesh. Eventually you cannot imagine yourself without it. The prison becomes familiar enough that somebody opening the door looks like a threat.
There is nothing sacred about a prison because you have lived there for years.
Mental illness can become an idol as easily as health can. Anything can become an idol once a person begins answering to it before God. "I cannot because i am ill" may sometimes be a simple fact, because illness genuinely limits people, but it can also become a creed repeated long after the question has changed. What can i still give? What can i still obey? Whom can i still love? What can i still learn? What can i still offer? If the answer is not nothing, then the enemy has not emptied you yet.
satan may have use for a wound, but he does not have ownership of it. He may turn suffering toward despair and God can turn the same suffering toward mercy, he may use isolation to make somebody hate mankind and God can make that person recognize loneliness in somebody everybody else overlooks, he may use shame to silence somebody and God can make the same person speak to somebody who thinks they are beyond forgiveness. The enemy can strike the material. He cannot dictate what God will make from what remains. There are things my own mind has done that i would never have chosen, and there are consequences i would remove immediately if God permitted me to remove them. Something is damaged and God still used it, something became sick and God still claimed work from it, years were not returned to me and He still found something in the years afterward. The enemy did not get everything he reached for.
Do not give it what it asks for
If your mind tells you that God has abandoned you, then let your knees answer before your feelings do. If shame tells you to hide, confess. If illness tells you everybody is your enemy, submit the thought to people whose judgment you trusted before you became unable to trust your own. If despair tells you nothing matters, perform the smallest duty in front of you as though it matters enormously. There are days when faith may feel less like consolation and more like refusing an occupying army another inch of ground.
I don't think God owes us an explanation for why one person's mind is quiet and another person's mind becomes a place of constant warfare. Job demanded answers and received something much larger than an explanation. Christ did not promise that following Him would make the road painless. We were told to watch, to pray, to endure, to deny ourselves, to take up the cross and follow. Somehow modern people hear all of that and are still surprised that sometimes obedience hurts.
Satan and his followers may find a thousand entrances into a wounded mind and spend years pressing the same places because they hurt every time. Then he can spend years discovering that the door still does not belong to him.
Deo Gratias.