grist to (one's) mill(redirected from grist to their mill)
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.