It's hardly yours. Using a custom domain for anything sensitive like banking is not a good idea. Your registrar is almost certainly a lot easier to phish/social engineer/whatever than Google.
Please don't spread unsourced FUD. I'm not saying registrars are perfect (although Gandi, which I linked, has an impeccable track record), but everyone uses registrars for their domain name, even the biggest businesses out there.
If you have a problem with a particular registrar, I invite you to source it and share it. But the general idea that the potential for a point of attack makes the email "not yours" is nonsensical.
What matters is the email address you give out to people. Where that email is stored and ends up doesn't matter. Which registrar owns the domain doesn't matter.
@pinboard has explained on Twitter that registrars can get tricked into letting an attacker into your domain account (of course they can). And from there they can update your zone file to send your mail wherever they want.
This isn't about the storage of your email.
Everyone uses registrars, but in some cases you can be your own registrar. Like in Finland, when .fi domain registrations were moved to exclusively to registrars (initially you would register domains with Finnish FCC equivalent, later option was added to let registrar handle that for you and finally it was moved to just registrars), quite a few companies and individuals registered to become registrar for .fi domain.
b) Who is going through all the trouble to target me specifically with a phishing attempt.