>>756968
You could say demonic possession is similar to mental illness. Mental illness enters the being through the flesh, it is a biological disfunction that causes the body to deteriorate quick and causes the soul to be confused or even incapacited (as it is the case for those who become vegetables for instance). It can be cured through material means, with medecine or surgery. If someone ends their life because of psychotic mental illness, they are not guilty of sin.
Demonic possession/oppression is similar except it enters the being through the soul. If we let ourselves be vulnerable, and we listen to the suggestions of demons, it can get to a point where we give the keys of our house to demons, so to speak. The soul deteriorates quick, it becomes unable to seek to fulfill its desires as it is the demons that decide what is to be seeked instead, and the body is confused or even incapacited, as it is not being controlled by ourself but by a third party.
Demonic influence is usually called oppression when our sensations, will, etc. are being forced onto a direction or another by the demons we opened the door to, and it is usually called possession when oppression has gone so far that one is simply not responsible anymore and the demons control them entirely (as much as an angelic being can influence a human anyway). This requires a spiritual solution, which is exorcism.
If someone ends their life because of demonic possession, they are not guilty of sin.
Mental illness is often a burden that we cannot choose or avoid, but demonic influence comes from letting oneself be vulnerable to demons (and those who are making terrifying progress in Christ will often be a more interesting target for demons).
Those who die lose their spirit, thus their body and soul dissociate and their soul goes to Hell while their body is left to deteriorate further. Those who die in Christ, however, are carried by the Holy Spirit and so, even if they appear to be dead, their soul is alive in Christ. Either way we will all be resurrected on the last day and receive eternal reward or punishment.
Demons cannot destroy your body or your soul, but they can influence you to use them in ways your sober mind does not want, and the worst case of demonic influence is called possession.