I just finished reading this whole thread!
Before I got saved, I was like 15 or 16. I went to sleep one night and got sleep paralysis. I didn't see anything at first but heard a very deep evil voice in my ear although I can't remember what was said. In my mind I was thinking it was trying to put my mind into confusion and make me insane. I think I had my eyes closed, but yet I saw an evil eye staring straight at me up close to my face. The eye's look told me everything - it HATED me and wanted me destroyed. It surprised me because, yes, this is the first time I've ever seen a real demon, but also because it hated me (like as if I did something personally offensive to it). I didn't know God then, but my parents would take me and my siblings to church when I was younger so I started praying the Lord's prayer.
I didn't even get to finish the prayer when I witnessed this:
In my spirit, I actually sensed that the powerful demon was frightened - not just frightened though. The demon was ASBOLUTELY TERRIFIED of the Lord!!!! And I didn't even know God as my Savior back then!
The demon fled and I felt the atmosphere lifted.
That was a pretty impactful event and ever since then I started to seek the Lord.
I got saved when I was 17 going on 18. If you read my "About" post, my walk with God was rocky for many years because of my hard-headedness but He got me through it. I can say that my walk with God now is healthy! (Thank you, Lord! ❤️)
But, for anyone who is being harassed by demons, please know that they are TERRIFIED of the Lord. God is a powerful, protective fortress and wants you to run to Him for safety. The key thing is to keep your eyes on the powerful Lord and remain abiding in Him.
Satan might lie to you and say "oh, you're not in His safekeeping (God can't protect you)" or "you don't deserve to be in His care" (this actually isn't a matter of deserving - we actually NEED Him so God WANTS to give His care to us). NONE of what Satan says is true. This is why you need to keep your eyes on the Lord and not look away from Him as the focus of your life.
When you get saved, God gives you the Holy Spirit as a seal that you belong to Him. But the Holy Spirit isn't just our seal over us - He actually causes us to change and grow into Christlikeness! That means, He will cause to overcome all the types of sin in your life, to be strong enough to overcome temptations.
The key thing is simply to ABIDE in the Lord. Keep Him consciously in focus throughout the day, bring Him into every decision that comes, ponder what He would do in whatever occasion comes your way. Resist the enemy (demonic oppression and tempation) in the Lord's power.
If you maintain abiding in the Lord, you'll keep your "house" from being invaded by demons wanting to return (or even new ones), and you'll keep from falling back into favorite besetting sins.
This is to be lifelong until we come home to the Lord or when He collects us. It's lifelong because when we've overcome one particular besetting sin, God will want to work in other areas of your life that need work.
-=<*>=-
There are special cases though. Sometimes people aren't able to come to Lord themselves. Like that paralyzed man who couldn't come to the Lord when He was in town. Fortunately, the paralytic had friends who dug a whole in the roof where the Lord was and lowered their friend to Jesus for healing (Luke 5:18-25). So we should help wherever another person can't help themselves.
-=<*>=-
Mental illness treatment is a consideration though. I'm a registered nurse and had to study mental illnesses in nursing school. Even though we aren't licensed to diagnose, we're taught to recognize certain conditions so that we can assist the doctor in the treatment he or she prescribes. I think it would be a good thing to have such professional counselling - especially if nothing I wrote about in the above is helping.
I'm writing this because spiritual harassment/oppression - in my experience - doesn't seem to last long if you bring it to the Lord and have it addressed. If you do everything the Lord tells you to do in obedience to His instructions (like abiding in Him and not resisting His work), then you'll be able to overcome the harassment and/or besetting sins pretty relatively quick.
This demonic harassment/oppression being posted about SHOULDN'T be taking over 10 years to resolve. So either the person isn't consistently abiding in the Lord and/or they need psychiatric help. Plus they keep adding to or changing their story. So...*shrug*.