File under “Regrets:” using the Gmail account I signed up for in spring 2005 for Google accounts. Impossible for me to have known that it would be impossible to maintain e.g. a YouTube account and change my email address all these years later. Annoyingly terrible account management.
Also: because I once had my domain email running through Google, my actual main email is apparently permanently in their system and cannot be used as an alternate email. “This address is already used with a Google account.” Except: it isn’t; I shut that down entirely months ago. 🙄