When the same phrase is used at the beginning of a series of sentences, that's anaphora. It's used to show emphasis in speech or writing — a popular tool for politicians, religious leaders, lyricists, and poets.
In Martin Luther King Jr's most famous speech, he said "I have a dream" eight different times. He used anaphora as a rhetorical technique, repeating the words to drive home a point. As a literary device, anaphora also gives emphasis and rhythm to lines like these of Charles Dickens: "It was the best of times, it was the worst of times," with the repetition of "it was" eight more times in one sentence. In Greek, anaphora means "a carrying back."