i do not believe that a person cannot lose his or her salvation.
as a christian i believe that i am the property of God. i belong to him and am in his possession. most would agree with me on this, but then they would say that: though it is not gods will that we fall away, we still have the choice to do so. first of all, how can your will to do something overpower gods will to do something else? if god wants to keep me in his fold, that is exactly where i am going to stay. if it were within my power to fall away by my own choice, that would mean god wasn't capable of keeping what belonged to him. it would be difficult to put my faith in such a god as that.