grist for/to somebody's mill

grist for (one's) mill

Something that initially seems bad or negative but is ultimately used in a positive way by someone. A: "The tabloids found out that you've been in rehab. How do you plan on handling it?" B: "It's just grist for my mill—I'm a changed man now, and that's what I'll tell the media. At least they're writing about me again!"

grist to (one's) mill

Something that initially seems bad or negative but is ultimately used in a positive way by someone. A: "The tabloids found out that you've been in rehab. How do you plan on handling it?" B: "It's just grist to my mill—I'm a changed man now, and that's what I'll tell the media. At least they're writing about me again!"

grist for/to somebody’s ˈmill

(of an experience, a piece of information, etc.) useful to somebody: As a novelist, I feel that any experience, good or bad, is grist to my mill.

Grist is corn that is is ready to be crushed in a mill in order to make flour.