I believe that we can choose to walk away from our salvation. Every person has his/her own free will. The Word says that we will know a tree by it's fruits. It also says that we are not to be a stumbling block for others. If a person has truly accepted Christ into his/her heart, he/she will want to live by the Word of God, striving for holiness and righteousnes, and choosing to do away with the "old way of life". Understanding, however, that people are at different levels of maturity in their walk with Christ.
I do not believe that we can live any way that we wish, do anything that we desire, willing and openly walk in disobedience and rebellion to God's Word, and then deceive ourselves into thinking we are saved. God's sees our most secret heart's desires. He knows if someone has truly accepted Him as Lord and Savior, and that is the determining factor.
