You probably do not want to announce your usernames to specific areas of our site or your site on a public forum.
A) Your MyGlow account manager/helpdesk username an email address.
B) Your forum username can be whatever you want it is of no consequence to your GlowHost account.
C) Your cPanel username is usually 8 characters and is not in the format of an email address and would have nothing to do with your login to our website. cPanel is part of your website.
Try using the lost password or lost username options next to the login thing found here:
http://glowhost.com/login/client.php