I don't see how a genuine believer could permanently stop believing either.
And that's why we should not project on to others our own determination to keep believing. We aren't everybody else. Just because we ourselves are determined to keep believing doesn't mean everybody else is. It was a big step for me in loving like God loves when I realized how wrong it is to project our feelings, likes, dislikes, etc. onto others. I mean that. I became a much more calm, patient, and tolerant person when I realized this. People are who
they are,
not who we are.
My faith is too engrained into me and I'm too convinced to ever completely stop believing.
And that is exactly the point. I learned that this matter of faith is not so much a matter of 'either, or' as it is 'strong vs. weak'. Some people don't have as strong of faith as you or I or somebody else,
but they have saving faith nonetheless. They struggle with different things. They have
different things they want and desire than us, and to
different degrees than us. To project our depth of faith and resistance to temptation onto others is simply wrong to do. We are not them, and they are not us.
If it was not for the Father drawing me and enabling me (John 6:44,65) I would have never come to believe in the first place (all glory to God!), so how could it be up to me to pull myself up by my own bootstraps and force myself to keep believing?
You can't. That's why believing won't last in a person
without God's help and encouragement. Which is why we can not boast either. It won't last without God in the picture encouraging us to keep believing.
Our walk of faith is like a child learning to walk
all the while his parents hold his hands in their's. Yes, the child himself walked, but not without the help of his parents that ultimately makes it happen. Our walk of faith only happens because of God's encouragement and power to help us walk the steps of faith, not walk those steps for us. It can't happen at all or for very long without God's encouragement. Our responsibility is to respond to his encouragement and be saved.
It think it quite naive at best to think once you become a believer you no longer have a responsibility to respond to God's encouragement (and warnings) because now that you believe you're programmed to automatically respond, and so you have been relieved of that responsibility. Time and testing will reveal this truth in the life of the believer. If you have strong faith, because you actively seek God through fellowship, Bible reading, worship, and prayer, you won't be so easily swayed away from believing when trials and doubts come. But if you have been in the habit of watching 'Game of Thrones', for example, or doing other wrong things outside of the Christian faith you will be easily swayed and more likely to fall when the time of testing comes.
It's all about strong faith vs. weak faith. We are to nurture strong faith within ourselves by living a lifestyle of God consciousness, not a worldly lifestyle, so that when our hour of testing comes we will persevere in our believing, not bail out and be lost on the Day of Judgment.