Hi Trusting, modern science tells us that it's likely that mental illness is no different than diabetes, heart disease and a whole host of other congenital disorders, and like them genetic factors play a big role in susceptibility. Instead of having a dodgy ticker you've got some sort of chemical imbalance or something like that. I really don't think that what you're suffering is some sort of satanic attack, you're definitely not demon possessed, Holy Spirit possessed definitely but not demon. That's not to say that it's beneath Satan to use your problems as a weapon against you, so we definitely need to pray about that.
From your post I would say you're doing all the right things, you're getting medical help and you're learning to distinguish between unhealthy weird thoughts from your everyday thoughts and putting your unhealthy thoughts into an archive in your head to be ignored and forgotten about.
I say, keep on keeping on. I'd also say keep on reading your Bible and if it goes a bit wonky put it down for an hour or two and go back to it. Chat to your pastor or vicar and see if he / she can ask a few church members to keep in touch with you and pray with you. Most important of all is to keep in touch with God, He'll get you through this and help you overcome.
Like any other physical condition, a really healthy diet avoiding processed meals stuffed with preservatives, flavorings, colours and other chemicals and lots of exercise will do no harm whatsoever.
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Dear Lord God, thank you, thank you, thank you that you have given us two amazing resources to get us past our problems so that we can focus our thoughts on adoration of you. Thank you for your Holy Spirit. I know that the mind is powerful but your Spirit Lord is so much more powerful. Father I pray that your Spirit will start a healing process in Trustworthy's head, so that he / she can carry on with his / her walk with you, enjoying the warm feeling and peace that comes with a closer walk with you.
I also for the Christian brothers and sisters in his / her circle. I pray that as he / she reaches out they will step up to the mark with plenty of love, deep friendship and support, emotionally and prayerfully.
We ask that you bring a full recovery to Trustworthy so that he / she can worship you, as you deserve.
Amen