What does the line mean -'put that thought away and looked at young trees sprinting, merry children spilling out of their homes'?

Dear Student,
In the poem, the poet has shown contrasting images of life and death. She has incorporated the image of the merry children, running out of their houses to play, in order to signify liveliness, vigor, health, beauty and happiness. This image is a sharp contrast to that of her mother who is nearing her death and has become old, inactive, weak and withered. 
Regards