11 Now faith is the reality^[a] of what is hoped for, the proof^[b] of what is not seen. (Hebrews 11:1 CSB)

Note that this scripture is very definitive in how it discusses faith. There is not ambiguous wording. It states that faith is the reality and proof.

I believe that, sometimes, people look at faith as something that can be put on or taken off. That based upon the situation we can choose to be faithful or not. And while yes, our free will does allow for us to make bad (non-faithful) choices our faith is not something we may set aside so lightly.

Scripture is very clear that once we believe that God will never leave nor forsake us. It is also clear that we cannot lose our faith. The only way to lose our faith after we have accepted Christ is to reject him completely. In this situation there would have to be reality and proof that we have rejected the savior.

Now, I am no theologian. So please search these things yourself and see what scripture says and what true theologians say. However, I do fully believe enough to state that faith is reality and proof of Christ’s salvation. Once and forever.