It's nothing to be concerned about actually and, you'll be glad to hear, you can remove this fear permanently in a few minutes if you wish.

What you've set up for yourself is known in Neuro Linguistic Programming (NLP) as an Anchor.

You can think of an anchor as being an association (deliberate or otherwise) between an emotional state and a subject.

For example, ever wonder why famous celebrities are used for advertising seemingly non-related products such as beauty products - even if they never use them? Companies will spend millions and millions trying to get those people seen with their products. It's because of the anchors that are created in people's minds.

Everytime you see the product, you automatically associate the product with the feelings that you generate when you think of the celebrity. If these are good feelings, you'll feel good about the product without even realizing it and you'll probably buy it next time you see it - and you probably won't even know why :)

That's why as soon as a celebrity becomes unpopular for some reason (e.g. involved in some kind of public scandal), the advertisers will usually drop them immediately from their campaigns...they don't want the feeling of scandal associated with their products.

Now what is important to realize about anchors is that they can be (and usually are) completely illogical and you won't even realize it. You'll just find a way to justify it to yourself and it will seem logical to you, even if everyone else thinks you are nuts :)

Ask someone who drinks Coke why they drink Coke, and not Pepsi instead, and they will come up with a seemingly rational explanation which they have justified to themselves. Similarly ask someone why they drink Pepsi instead of Coke and you'll get the same result.

But if you truly examine the fundamental reasons - probing back to their first association with the product - you'll often find it can be something as nonsensical as because their dad or best friend drank it, or they first drank it when they were at a happy birthday party, or they noticed a famous person drink it on the TV, or whatever.

From a rational perspective, the reason will be totally illogical - they are just two ordinary Cola drinks, after all :)

Again, it's about the anchors that have been set up.

For an anchor to be created successfully, there must be a strong initial emotional reaction to something - and this often happens in childhood - followed by occasional re-triggering.

If you look at your case, that strong emotional reaction was there when your dad bought the game and you heard those screaming noises. You anchored fears you had within yourself when you were 6-years-old to the monsters in the game.

And often one of the greatest fears within young children is the fear of the dark - darkness causes you to lose a vital physical sense (sight) that you depend on constantly so there is inherent uncertainty about it. Darkness has become part of that anchor for you.

So now it's natural that these anchors are being retriggered when it is dark, or perhaps when you re-experience uncertainty, and you need to keep turning on the light to deactivate them again.

As I said at the start, breaking anchors is actually pretty easy once you have identified them.

One highly effective method is Tony Robbin's Swish Pattern.

Another highly effective method is EFT, especially the Faster EFT variation, where you just bring up the emotion that the anchor triggers and deliberately neutralize it.

Once you've neutralized the anchor, you'll wonder what all the fuss was about :)

Hope that helps :)