Related and possible duplicates: https://english.stackexchange.com/a/66994 https://english.stackexchange.com/a/197194 https://english.stackexchange.com/a/93947 https://english.stackexchange.com/a/95849 https://english.stackexchange.com/a/305413 https://english.stackexchange.com/a/361016
– tchristDec 29 '18 at 18:28
Rules of grammar are not very useful for giving sudden warnings. If there's only time for one word, don't make it an auxiliary verb.
– John LawlerDec 29 '18 at 20:02