Consider these sentences:
The reader can reasonably be expected to know that hats are worn on the head, as opposed to the knee, wrist, ankle, or elsewhere. Moreover, unless your story is about reincarnation, a person has no other lives in which to do something like that.John removed his hat from his head.Joan had never done something like this before in her life.
John removed his hat
from his head.
Joan had never done something like this before
in her life.
This is an easy thing to find and fix. The easiest and best editing is often done with just the delete key.
I think that well written prose is something like a Japanese painting where each stroke of the brush contributes to the picture with nothing extraneous added. Remove everything that is not needed and no more. You know what should be conveyed to the your target reading audience. That knowledge should reflect what you put on to the page.
What went without saying to a serious adult was lost on a callow youth such as myself. Some cultural referents may be missing from your audience. What is obvious to an American reader may fly over the head of a British reader. or vice versa.
You may cut too much, but this is the exception, not the rule. If there are two things in your prose that support the same point, look for the one which best makes your point and cut the rest. If there's something your reader can reasonably infer from the rest, delete it. Every word must contribute enough to the story to justify the reader's time spent reading it.