merging different accounts
I set up an account a long time ago under email@example.com (user digialdiague). When I log into that account it asks me to log into a different account and I usually log into my work account (firstname.lastname@example.org).
I wanted to use my personal account for personal things so I created a third account email@example.com but now I realize that was probably a mistake because it won't accept my public key (I already uploaded it for the other account).
I would like to merge my firstname.lastname@example.org account with my email@example.com account and keep my work account separate. I would also like to be able to use the same SSH key for all the accounts.
How do I do that?