I'm not afraid of the dark and usually I need total dark to sleep. However, many people are afraid of the dark.
I have a friend who is NT, an ex air force officer who was in Desert Storm and in the middle east a lot and in dangerous situations, and she won't sleep in the dark unless she has to.
When she came to stay with me for a week or so last year (granted, she had just been through a horrible experience, but that didn't effect her aversion to dark) she would sleep with the light on, the bedroom door closed and the closet doors open. No curtains or blankets could hang on the floor. I do not know why. That's just her thing. She was like that when we were kids and it was always hard spending the night with her because she would insist on a light. After the crisis she had gone through and while staying with me, she didn't want to sleep alone so she asked me to sleep with her. No problem, I went to spend the night at her house or her at mine a lot when we were in school. Girls aren't usually as funny about sleeping in the same bed as boys are. I didn't mind sleeping with her because she's a good sleeper and doesn't kick or steal covers or snore, but the damn light drove me nuts.
A few months later when I went to visit her at her house, she still slept with the light on. Her bf (she had got back with her high school bf) hated it, but he dealt with it by buying a sleep mask. She had a guest room that I slept in so it was dark in there. Except for the one night we sat up late talking and listening to old music and she slept in there with me. We had a "retro school days night" because her guest room was furnished with the white canopy bed with pink canopy and white bedroom furniture she had when she was growing up, so it was sort of cool to "go back in time".
It's normal. I wouldn't worry about being afraid of the dark unless you truly believe that something specific is actually there in the dark to get you. Not that it might be or that it could be, everybody thinks that from time to time, but a real belief in some sort of boogyman that you are sure is there when it's dark. If that's the case, I'd suggest talking to a therapist who can help you realize that there isn't one.
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I'm giving it another shot. We will see.
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