Upgrading via WordPress Dashboard..

Hey,
Recently, I have been trouble updating my wordpress via the wordpress dashboard. It used to do it without a problem but now it tells me it fails because it was unable to create /public_html. I updated it myself via the FTP (Downloading it and overwriting all of the old files etc..) but for the future, I was wondering how to fix this so I will be able to upgrade via the dashboard.

Thank you!