Trying to be holy is the same thing as being under the law. I was always trying to be a fit vessel. I was told that the Lord could not use me if I was not a fit vessel. The law promotes sin, Romans 7:8. What I didn't know is that I was already a fit vessel "In Christ". They didn't tell me that.
The teaching is anti-Christ and anti-Gospel we never become fit vessels. You are right when you say that holiness and righteousness are done out of a heart of thanksgiving and gratitude for what Christ has done for us. We do it because we love him, not to be accepted. We are already accepted "In Christ". We have the same Spirit.