They just know.

No one knows what goes inside your head,
even when you try to explain it
using the most simplest word,
using a gazillion words,
using pictures,
using signals,
using colours to describe them,
using what ever language you can ever think of, or
using anything for that matter

but,

to find a person that knows what actually is in your little brain, would be awesome eh?
And that person is not your own mother, of course.
Just that one person who can tell you what you are thinking, without having to guess because they know.

They just know.