I suffered insomnia for years (5+ years for sure). I had very poor sleep hygiene. I went sleep at 2 am, and woke up at 11 am. I felt tired at work and I drank coffee everyday. I was coffee-maniac, and coffee effectively destroyed quality of my sleep.

So you see that I spent about 9 hours in bed and I had very bad sleep quality.

A few months ago, I started learn a lot of stuff about sleep. Most of what I read on the internet was useless.

But I found in academic sources (i.e. inside ".edu" and ".gov" domains) two very important concepts (they tightly connected to each other):

1. Sleep effectiveness;

2. Sleep restriction;

You can get idea about them here:

https://en.wikipedia.org/wiki/Sleep_restriction

I started to follow very strict sleep schedule.

1. I go to bed in the interval between 21:15 - 21:50

2. I wake up in the interval between 06:00 - 06:03

Note that my wake up time is strictly fixed.

Now I spend even less time in bed (21:50 - 06:00), but I feel much, much, much better. As my fitbit shows me, I have much less interruptions during the night.