Why did Frodo Volunteer to take the Ring?

[Maédhros]

I know that Frodo had a calling of sorts to take the Ring, but how much do you think it was a higher purpose and how much was his own desire to keep the Ring.
Why would he volunteer to take on a quest to destroy the Ring, when he couldn't even do it in Bag End.
From LOTR: The Shadow of the Past

Gandalf laughed grimly. ‘You see? Already you too, Frodo, cannot easily let it go, nor will to damage it. And I could not “make” you - except by force, which would break your mind.

It leaves me wondering.