Here's a photo excerpt that shows a bad case of oversharpening. You can easily spot the light stripes on the edges of the petals.

As so many of our tips, this one begins with duplicating the original layer. Click Layer/Duplicate Layer, or drag the existing layer upon the Create New Layer icon on the Layers palette. Now take the Filter/Other/High Pass effect, already a distinguished tool for sharpening, and set a low value in the appearing dialog, say, about 1 to 2. You shouldn't set a too high value, just about the width of the contrasty edges. If you choose a high value for High Pass, the softening will be too strong. Similarly, an unreasonably low value leads to no significant change. A value of 1 to 2 is usually appropriate. We have used 1.0.

We don't need the colors from the changed layer, just a black-and-white mask, so click Image/Adjustments/Desaturate (or press Shift+Ctrl+U) and turn the layer into B&W.

As the softening requires the inverse of the colorless mask you now have, proceed with Image/Adjustments/Invert (or Ctrl+I)

On the Layers palette, choose Hard Light instead of Normal. If you want a less radical result, you can select Overlay, or, for an even softer blur, Soft Light. It doesn't matter if, after selecting Hard Light, the change looks a bit drastic as you can refine it later by setting Opacity.

Change Opacity to a lower value for this refining. In this particular case, a value around 35% looked optimal. Finally, click Layer/Flatten Image to merge the layers.

Compare the result to the original photo to spot the difference. By zooming the picture, you can also see that the small details haven't vanished as the result of the softening, only the edge contrasts have diminished.

Before / After