We all make mistakes, but luckily WordPress has our backs. There is a built in backup system that makes a copy of the page or post every time you hit update allowing you to easily revert to a previous version.
1. In order to access the post revisions, press on the [Revisions] button on the right hand side of any post that has been edited.
2. You’ll now be able to see the current and previous version side by side, to see previous versions use the slider at the top and to revert back to the previous version click the [Restore This Revision] button