You can surely "opt out" by committing deadly sin..there is no forcing by God to stay in this relationship. And that is what it is, a relationship with God.
It is more than just a relationship. You become a new creation.
“6And I am sure of this, that he who began a good work in you will bring it to completion at the day of Jesus Christ...” - Phil 1
“By the which will we are sanctified through the offering of the body of Jesus Christ ONCE FOR ALL...But this man, after he had offered ONE SACRIFICE FOR SINS FOREVER, sat down on the right hand of God...for by ONE OFFERING he hath perfected FOREVER them that are sanctified”. (Hebrews 10:10,12,14).
If you 'opt out' you were never IN the faith to begin with:
I John 2:19 - They went out from us, but they were not really of us; for if they had been of us, they would have remained with us; but they went out, so that it would be shown that they all are not of us.