It is hard to edit your own work. That being said, the answer will depend on how large the work is.
An example: A short story under 6,000 words can be put aside for a few days and easily scanned for blatant errors.
Novellas, or works exceeding 30,000 words, should be put aside for a full month before any editing is attempted.
The real answer you are looking for is: You cannot truly edit your own work.
To polish your work it goes through many rewrites and critiques. This will make the story very familiar to you. When this happens, your brain will disregard errors, and you will read your work skipping over the errors.
What to do:
Complete your rewrites until you have polished your story/novella/novel. Usually 6 or more rewrites will be needed. Once that is complete, search out a good editor. Don't go cheap on this step. Editing is important, and there are several different types of editing you can get. They range from simple editing (spelling and grammar checking), to line editing (following the story line for consistency).
Poor editing sticks out and makes a person put your hard work down. If you are serious about writing, follow the steps and have a polished work available for your audience.