We may not like it, but there are absolutes in this world. One which comes to mind is death. Regardless of how well we take care of our bodies, they are not immortal. Another is if you deprive yourself of food and water permanently, you will die, you can only exist so long without oxygen and so forth. If this happens than that will happen. It is a part of natural law.
Now granted, there are factors that can be introduced which have an impact on the outcome. In your weakened state you decide that it was a bad idea to abstain permanently from food and water and you decide to forsake that idea. There is a point where you can change your mind, change your behavior and you will survive. If you don't change your behavior, you will suffer a premature death.
The same thing applies to us spiritually. Because of sin, we are spiritually dead. God, in His great love, mercy and grace has provided us with bread and water of life, Jesus Christ and though we are "dead", gives us the ability to receive or reject it. If we reject it we will remain spiritually dead but if we receive it... there was a reason that Jesus said He was the resurrection and the life! (John 11:25)
How do I know this is so? It is not because someone told me it was true. It is because I have tested it and found it to be true.