Hebrews 12:11

The writer to the Hebrews has just compared the trials his readers are enduring to a father's discipline of a beloved child (verses 5–10), not punishment for its own sake, but training meant to shape character. Here he names the honest difficulty of that: no discipline, however good its aim, feels good while it is happening. The Greek word behind “grievous” carries the sense of sorrow or grief, not mere inconvenience.

But the verse doesn't end in the pain. “Afterward” is the hinge word; there is a harvest on the far side of the hard season, and it comes specifically “to those who have been trained by it,” using an image (gymnazo) drawn from athletic training: discipline that is worked through, not merely endured, produces “the peaceful fruit of righteousness.”