The biggest mistake people make when using an abrasive grit whether it be diamond or sand paper is as mentioned above, too much pressure. Also, make sure you are traveling the edge the distane of the sharpening stone. In other words short strokes makes it harder to sharpen.
If your diamond stone is 6 inches long, use all of it you can, and rotate sides between strokes unless using a file. But what ever you use efinately lighten up each times you change sides and decrease licks, or use very light pressure cause the new sharpening blocks,stones, files, etc..., are extremely hard and to much pressure causes the edge to be dulled instead of sharpened.
God Bless