Is that because you are stuck on works based salvation?
>>Lets say a humble saved person commits a mortal sin - what then?<<
Again, works based? You see, when Jesus paid the price it was paid in total. We are not yet in our perfected bodies.
Romans 7:14 For we know that the law is spiritual: but I am carnal, sold under sin. 15 For that which I do I allow not: for what I would, that do I not; but what I hate, that do I. 16 If then I do that which I would not, I consent unto the law that it is good. 17 Now then it is no more I that do it, but sin that dwelleth in me. 18 For I know that in me (that is, in my flesh,) dwelleth no good thing: for to will is present with me; but how to perform that which is good I find not. 19 For the good that I would I do not: but the evil which I would not, that I do. 20 Now if I do that I would not, it is no more I that do it, but sin that dwelleth in me. 21 I find then a law, that, when I would do good, evil is present with me. 22 For I delight in the law of God after the inward man: 23 But I see another law in my members, warring against the law of my mind, and bringing me into captivity to the law of sin which is in my members. 24 O wretched man that I am! who shall deliver me from the body of this death? 25 I thank God through Jesus Christ our Lord. So then with the mind I myself serve the law of God; but with the flesh the law of sin.
What then? We have been forgiven. That is not to say that we do not strive to refrain from sin but we do understand that we are still in our carnal body. Once again, a reason for total humility understanding it is not we who earn our salvation in any way.
The “mortal sin” that the “saved person” commits was “already” paid for by the Alpha and Omega.
And he will be forgiven it if he repents.