WordPress has a great revisioning system that auto-saves your post as you’re working with it. It also allows you to save different drafts and go back to an older one if you want to. Although this is great, the number of revisions often gets carried away, which takes up some database space.
You can easily limit the number of revisions allowed by adding this to
<?php # Maximum 5 revisions # define('WP_POST_REVISIONS', 5); # Disable revisions # define('WP_POST_REVISIONS', false); ?>