If you are just an cPanel end-user, you should really be contacting your hosting provider on such issues.
Without knowing what files you have in your home directory and what you are using your account for, all I could suggest is that you delete all files that are not needed!
More specifically:
1. If you access your mail via IMAP, delete all unnecessary sent messages, drafts and delete the contents of trash folders
2. If you have any form of server-side spambox, empty it
3. Delete any files of which your website is comprised that are not needed - obsoleted image files, for example