Strange thing

Today,When I wanted replied my Coach a question in English,I wrote a sentence that is “It’s a great thing itself”.When I wrote the sentence before,I don’t thought the “itself”,The word even didn’t have came out in my brain,but when I wrote down the sentence,The word came out in my brain,I had a compulsion that is add the “itself”at the end.It was strange,I didn’t found the word,Actually,It was came out in my brain unconsciously.I remember that I saw the word from another sentences many time,I forget where I saw it.But it stay in my brain,Even though,I did not conscious to remember it.This is not only thing,I met many things like this.I don’t have consciously remember something,But when I meet it many times,It will stay in my brain.Learning the language seem can’t stop.