what is the meaning of the following Idiomatic expression, " I did not see it coming" and " stabbed in the back"​

For the module essay you will write four paragraphs. • in paragraph 1, state one theme a reader can find in twelfth night and explain why it is good advice for the characters in the story • in paragraph 2, describe an event in the play, and explain how one of the characters' actions illustrates the theme • in paragraph 3. describe another event in the play, and explain how one of the characters' actions illustrates the theme • in paragraph 4. restate the theme, and explain why it is good advice for the reader and ons and you may write about either of the following themes (choose only one) • true love with a little from fortune triumphs over man's folly • troubles come and go don't take things too seriously