Although salvation is a work of God and not of ourselves, it's important to remember our role in believing. When someone hears the gospel message clearly and receives Christ, that person is coming into agreement with the terms of the covenant. The terms of the covenant includes, continuing to believe just as from the beginning.
As for you, let that abide in you which you heard from the beginning. If what you heard from the beginning abides in you, you also will abide in the Son and in the Father. - 1John 2:24