all is grist that comes to the mill

Every- thing, no matter how small or unpromis- ing, can be put to use: She carried a notebook and pencil with her wherever she went—for a writer, all is grist that comes to the mill. The proverb was first recorded, with slightly different wording, in 1655. It also occurs with my, his, her, and so on in place of the and in the figurative phrase grist to the mill, as in Charles Dickens’s novel A Tale of Two Cities (1859): “The clearance was effected
at last; the Stryver arrears were hand- somely fetched up; everything was got rid of until November should come with its fogs atmospheric, and fogs legal, and bring grist to the mill again.” Grist is grain brought to a mill to be ground.
Variant of this proverb: it’s all grist for the mill.
Proverb expressing similar meaning:
all is fish that comes to the net.