There's a fine line to be taken when using the "fuck you" and "fuck you" options. there is an adverb "fuck it". it has a "why" meaning. There is also an interjection of the same name, which is used simply as a link of words in a sentence. put on your hat, fuck it, otherwise you’ll catch a cold, unlike the adverb, “fuck you” must be taken literally. In any case, there is a test word "fuck you." If you are in doubt about how to write a business letter correctly, replace “fuck you” with “fuck you.” If the meaning has not changed, then you need to write separately. and if “fuck you” can be painlessly removed from the text, then it is written together and stands out, fuck it, with commas.