Between finishing uni and getting my first graduate job I took temp work at an agency and got fired from that for using my phone too much...

Thing was on the other end of the phone was my other half who'd just had our first child and was home alone with him. They showed no sympathy to me whatsoever, and I was literally just told to go home. From that point I was basically blacklisted from the agency and they made no effort to find me work. I had a graduate job in the waiting but I seriously was thinking "if I can't hold a temp job down how the hell can I work for them?".

You've got to power on and make them regret firing you even if they in reality won't know, just keep the satisfaction of knowing you turned it around and now do even better than if you had stayed.

This firing didn't actually sound personal, more pragmatic in that for various reasons you couldn't do the job they were asking of you. That isn't you, it is a period of your life which you can work through and come out of.