judging distance?
You might be doing the same thing I still find myself doing at times, concentrating so hard on the plane that everything else loses perspective.
Try shifting your focus breifly to the end of the field during the landing. I think this tends to open up your field of vision making landings a lot better/easier.
I still have to do this when flying a new plane for the first couple times or if I am flying at a new field.
Ed M.