When you think about it, it makes sense. As you're home alone, someone or something could be lurking around your house at any given time. Of course, you aren't keen to check it out.
So you ignore it.
Much like when you take a shower and close your eyes to avoid getting shampoo in them, you feel vulnerable.
Much like when your eyes open after those fleeting moments of leaving your guard down and the anxiety just gets worse as you gaze upon the drawn curtains to your right.
They're drawn, like your eyes are to it. Because you sense a presence beyond them, as if an entity was using it for refuge. An entity that failed its task once again.
Of course, you could draw back the curtains and reveal the existence of this being. But you aren't very keen on doing so, so you ignore it.
When you think about it, it materializes. Much like when you sit by the computer, and the clock strikes 3 AM.
You go through all the hiding spots in your mind that you've deduced it has around your residence. The curtains being only one of them. You know it likes corners and rooms without light as well.
It likes areas where it can't be spotted by the limited range of a humans eyesight. Those are its favorite. With this information, you could attempt to ambush it and cast it away for good.
But you aren't keen to do that, so you ignore it.
In fact, not thinking about it nullifies the 50/50 chance of its existence. You're okay with it being real, and being a figment of your imagination. But not one or the other.
If it's real, then it's out to get you. If it's made up, you're going to feel really stupid. If it's both, you're neither right nor wrong. So you ignore it.
Therefore it lives on as both as long as you don't take the time to acknowledge it.
But there was one slight error in your logic. By taking the time to consider your potential actions, you thought about it. You could've just ignored it, like you did with everything else.
Instead you validated its existence. So, before you go any further, remember this...
When you think about it, it's there.