Jason/Castiel
The vessel I currently reside in belonged to a man named Jimmy Novak. He was very devout and prayed nightly to be of service to the Lord. When I came to Earth to aide in protecting the 66 seals, I needed a human body to occupy. Jimmy agreed to host me in his.
This vessel has since been destroyed and Jimmy's soul has gone to heaven. When the vessel was put back together, I reclaimed it. It is now only a vessel with no soul and if I stopped inhabiting it, it would be just a dead body.
Angels can't possess someone without their permission. This vessel was given over to me freely. Though the outcome for Jimmy Novak was regrettable, he was a very devout man and his vessel is strong.