Our blood is a river of life flowing inside of us - it's a wonderful,  amazing thing really. But notice- without the heart to pump the blood, it would cease to flow and we would die because "the life is in the blood". But the only thing our blood keeps alive is our fleshly bodies. To keep our spiritual self alive, our spiritual body,  we need the Holy Spirit flowing inside us, again, like a river. And just like our blood, it's our heart that keeps the Holy Spirit flowing - a soft heart. Depending on our heart's condition; the Holy Spirit's flow within us can be a mighty, raging flow or a tiny trickle. It can even cease. In which case we die, spiritually.  Our hearts can be, spiritually, stone or flesh. They can be "stony" ,that is to say, full of stones, that people have thrown at us, and that we in turn pick up and use to throw at people. We can break up the fallow ground,  fortunately.  We can God mend our broken hearts - we can let Him change our heart's condition by letting Him in - by letting Him flow in us as a river - for that river will take those stones of offence, and some it will sweep away in it's life-giving flow, while others it will smooth over the passage of time - even polish them and make them look beautiful: what once hurt us now becomes a jewel in our crown of glory - that we can then pick up and use to defeat our enemy, our Goliath, when he dares to challenge us. 

So having the Holy Spirit flow in us is as essential to our eternal life as our blood is to our fleshly, mortal life. Without the Holy Spirit the written Word of God is our death, for it brings condemnation to all that are not submitted to Him, for our protection,  for our good. To serve us as a loving father would, who has made us able ministers of the New Covenant, not of the letter, but of the Spirit: for the letter (written word) kills but the Spirit (spoken word) gives life. Unless the Holy Spirit speaks the written word to you (reveals), it will not save you, but condemn you.

Think of that breath you just breathed. It gave you another few moments of life, by oxygenating your blood - which then carried it throughout your body. Something outside you came inside you and gave you life. Likewise,  the Holy Spirit "oxygenates" the blood of Jesus- the Word of God, in us, keeping us alive, spiritually, with true, eternal life. Our flesh, thank God, is the only part of us that is not eternal - it is the part of us that God in His mercy allows to take the full brunt of our sin and rebellion, so that when our flesh dies, all that resisted and rebelled against God dies with it. Our flesh does not profit us for the life therein is temporary, mortal, but a passing fancy, quickly fading. It is our spirit that profits us - for it is our spirits that carry His Word and it is His Word that grants us true life BECAUSE HE SAID SO. Because all He says is true - eternally true. So when His Word says -  of us, "I give them eternal life; and they shall never perish" we know it's true because HE SAID IT, for He is the Way, the TRUTH and the Life. He has power over all flesh so He can give eternal life to as many as have been given to Him. And this is life eternal, that they might know You the only true God and Jesus Christ, whom you have sent. Knowing the word is not the same as Him knowing you. Those whom He knows will abide forever with Him. So, our eternal fate is sure - because He said it is, and as anyone who has read Genesis chapter One can testify - all He says comes to pass.

It is the Spirit that quickeneth, the flesh profiteth nothing (quickeneth: To cause to come alive, to receive life). Does not our body testify to these truths? And there are three that bear witness  in earth (in flesh): the Spirit, and the Water, and the blood: and these three agree in one. We cannot remain alive without 1) Water 2) blood and 3) air. Likewise, we cannot remain alive eternally without 1) the Word of God 2) the Blood of God and 3) the Holy Spirit of God. These three quickeneth us - not our mortal flesh, brethren. We might as well give our flesh to God to consume as a pleasing sacrifice on the altar of His daily will for us, for it's dying anyway! Why cling to something that's dead? Yet so many do. They choose death, thinking it's life and they reject life thinking it's death. They're thoroughly deceived.