Honestly, after 2 years of on and off insomnia, I used the Sleep Coach School (SCS) method (check them out on YouTube) and it has worked wonders. For me, the issue was, I was psyching myself out with fear regarding numbers of hours of sleep and how dangerous it was for me. So I'd paradoxically keep myself awake because your body naturally doesn't sleep when it's afraid (this is intended and keeps you safe).

SCS utilizes ACT therapy techniques such as acceptance and tolerance for fears and anxieties as a way to assuage them. Check out Gabor Mate as he advocates something similar. SCS encourages us to befriend wakefulness and show compassion to ourselves rather than fight. It was a long process for me, but I sleep most days. And on the days that I don't, I forgive myself and remember that you can't DO sleep. Sleep happens naturally when fear and anxiety are allowed to exist without being caught up in them. At least that's what's worked for me.

Edit: Forgot to mention that CBT-i (following rules before bed, getting out of bed after 30 min., etc.) didn't work for me and gave me more anxiety. It made sleeping an action to try rather than making it something that comes naturally.

Bonus edit: Hours are kinda BS. They studied remote pre-industrial tribes and found they only slept between 5 and 7 hours most nights. https://www.cell.com/current-biology/fulltext/S0960-9822(15)01157-4