At the end of Nikki Giovanni's "Mothers," after reproducing the poem she was taught by her mother and saying that she has taught the same poem to her son, the speaker adds that he has now recited it to his grandmother:
Just to say we must learn
to bear the pleasures
as we have borne the pains.
This is the importance of the poem being passed down through three generations, and perhaps more. Parents pass on abuse to children, generally without meaning to do so. As Philip Larkin puts it, "Man hands on misery to man." Giovanni acknowledges this, saying that there are "pleasantries and unpleasantries" in her relations with her mother. However, since one cannot help handing on some negative qualities and experiences, it is important to make a conscious effort also to hand on such things as poetry and good memories.
The poem itself is, in this instance, less important for the author than the memory that surrounds it. She could easily have taught her son a poem out of a book, and this might well have possessed more intrinsic aesthetic value. What it would not have had is the story of the child out of bed at night, perhaps expecting a reprimand from her mother, and experiencing instead a memorable moment of connection which grounds the poem forever in her own experience.