...Meaning: if i am alone somewhere, i need at least a tiny illumination in the room to sleep (unless it is impossible for any reason like no electricity)

Now, for the most difficult part: i am afraid of "ghosts"
Right. Or whatever.
The house is closed, i have window bars for every window and curtains, and it is very unlikely for someone to enter the house
I live in a city, not in the woods

But I am still keeping a light on
I had to choose specific light bulbs to reduce consumption

I have to say, i was able rarely to sleep alone in total darkness on rare occasions when I was more relaxed, but normally i am... "afraid" and wake up again to switch on a small light

I had experiences of sleepy paralisys that were prolly worst with light on

If everyone else has this and wants to share any thought, i'd like to read it