Repetition plays an important role right from the beginning of "Wild Geese," as the speaker uses an anaphora in the first two lines:
You do not have to be good.
You do not have to walk on your knees
This anaphora makes the speaker sound insistent. Repeating the phrase "You do not have to," the speaker reassures readers that it's not necessary to meet society's rigid expectations—even though it might be hard to believe that at first. This anaphora is also just plain musical, giving these opening lines a hypnotic rhythm that urges the reader into the poem.
The speaker uses another important anaphora later on, repeating the word "meanwhile" in lines 7 and 8:
Meanwhile the world goes on.
Meanwhile the sun and the clear pebbles of the rain [...]
This repetition (and its return in line 12: "Meanwhile the wild geese, high in the clean blue air, / are heading home again") reminds readers that the world goes on even while people are hung up on their own "despair." These repeated "meanwhile[s]" suggest the vastness of all that goes on in the world, all the time, even when people are focused on their own petty problems: so much can fit into that "meanwhile"!
The speaker also uses subtler forms of repetition. For example, line 5 features epanalepsis, since the speaker uses the word "love" at the beginning and end of the line: "love what it loves." Here, the repetition suggests the ease and naturalness of love for the "soft animal of your body." Meanwhile, the diacope of line 17 ("over and over announcing your place / in the family of things") echoes the wild geese's rhythmic calling as they fly overhead.
Repetition thus lends the poem both music and meaning, creating harmonious rhythms and drawing attention to big ideas.