When we edit our work, I think it's very easy to sit within a confined range of known and often used tones. We have what I would describe as a tone comfort-zone, one which we have settled into and tend to apply to most of our work.
Part of this is due to visual awareness issues, of not really thinking about luminance in the first place. We think of our images more in terms of scenery - mountains, rivers, grass, rocks, whatever. But we haven't passed this early stage and moved on to thinking about these subjects less as what they are, but what they provide in terms of luminance and other tonal qualities.
Indeed, our edits can be rather narrow in their tonal range, just like our vocabulary is narrow when we first learn to speak. We have to move outside of our comfort zone at some point, but this can be difficult if we're not really aware of what's out there and how luminance levels in the far brighter and darker regions of our images may serve us.
One technique I use is to push the luminance to extremes and then reign it back until I think it looks good. It's well known that if you move something to where you think it should be and compare that to where you would have ended up if you pushed it well beyond where you think it should be and move it back, your initial judgement will have been conservative. In other words, by really going over the score and then moving it back to where you think it should be, you'll find you've pushed the boundaries in your edits.
We all have our visual comfort zones and it's good to try to move beyond them. The only way to do that is to exercise your visual awareness by placing yourself at the extremes well outside the normal parameters that you reside, and see how the new terrain fits.
Our visual sense needs to be exercised for us to learn to truly see what is possible, and this is one such way to do it.