In the early Chapters of the Fourth Gospel, Jesus repeatedly tries to explain the nature of his 'mission' - what he brings - using a contrast between water on the one hand, and that which water becomes through following Jesus after death: spirit or some other.
More exactly; Jesus uses "water" to mean this life, this temporary life in this mortal world - and contrasts it with what he offers - which is "not of this world".
Indeed, throughout the Fourth Gospel, involving everybody from the disciples through to Pilate, we can see Jesus struggling (over and again) to make people understand that what he offers is not of this world; that he is not a would-be "king" who claims to offers a better life in this realm of "water" in which everything is temporary...
Instead of that; Jesus describes the Kingdom of life-everlasting coming after death, and only after death: to reach it we must first die, and then be 'reborn', born-again - that is resurrected.
In Chapter 1, John says that he himself baptizes with water - but Jesus's is a baptism of the spirit - which refers to the distinction between this and the next world, the spirit being from Heaven:
And John bare record, saying, I saw the Spirit descending from heaven like a dove, and it abode upon him. And I knew him not: but he that sent me to baptize with water, the same said unto me, Upon whom thou shalt see the Spirit descending, and remaining on him, the same is he which baptizeth with the Holy Ghost.
In Chapter 2, the contrast is given in the nature of the water-to-wine miracle of Cana; where water is perhaps understandable as this-worldly life, and "wine" may be taken to stand for the transformed life after death.
In Chapter 3; Jesus talks to Nicodemus about being "born again" - which means first to die and then to be resurrected - i.e. a kind of rebirth, but into an everlasting condition:
Jesus answered, Verily, verily, I say unto thee, Except a man be born of water and of the Spirit, he cannot enter into the kingdom of God. That which is born of the flesh is flesh; and that which is born of the Spirit is spirit.
Here we see "water" of this life, again contrasted with the "Spirit" of the next. And again that the Spirit must be preceded by the water. Man must first be born into this mortal world (of "water") if he wishes ultimately to enter the eternal kingdom of God.
Jesus also introduces a further "analogy" for this mortal life as "the flesh" - to explain that there is no possibility of achieving the Kingdom of God on earth and in this mortal life; but only by passing-through death and re-birth ("Except a man be born again, he cannot see the kingdom of God).
A man that is born into this mortal world of the flesh can only be mortal ("the flesh is flesh"); but he that is re-born (i.e. resurrected) into the world of Spirit, beyond death, will himself partake of the immortality of that life-after-life ("the Spirit is spirit").
In sum; for a man to become eternal he must be born (that is, re-born; which entails mortally-dying first) in the eternal world.
Chapter 4 describes Jesus at Jacob's well, talking with a Samaritan woman who is drawing water.
Again Jesus contrasts the water of this mortal and temporary life which the woman draws from the well, with what He Himself brings to the world: which is everlasting water ("living" water - i.e. by analogy life that is eternally-self-renewing) - for those who desire it, and ask for it.
Jesus answered and said unto her, If thou knewest the gift of God, and who it is that saith to thee, Give me to drink; thou wouldest have asked of him, and he would have given thee living water.
The woman saith unto him, Sir, thou hast nothing to draw with, and the well is deep: from whence then hast thou that living water? Art thou greater than our father Jacob, which gave us the well, and drank thereof himself, and his children, and his cattle?
Jesus answered and said unto her, Whosoever drinketh of this water shall thirst again: But whosoever drinketh of the water that I shall give him shall never thirst; but the water that I shall give him shall be in him a well of water springing up into everlasting life.
In Chapter 5, Jesus goes to the pool at Bethesda, where the "impotent" seek to enter the water and be healed. The "impotent" implies all men in this mortal life and world.
In this world, therefore temporarily. Jesus heals the man ("Take up thy bed, and walk") but Jesus explains that what he has come to do is not about temporary healing in this temporary world; but is about "sin" (by which, in the Fourth Gospel, Jesus mostly means death without resurrection).
Afterward Jesus findeth him in the temple, and said unto him, Behold, thou art made whole: sin no more...
I think that Jesus's admonitions - here, and sometimes elsewhere - to sin no more, or not to sin, make no sense if understood as ordering people to cease from moral transgression - which Jesus knew (as we know) to be an impossibility in this mortal life.
"Sin no more" - in the Fourth Gospel - means (more or less) that people should die no more; that is, that they should instead understand, believe, and accept Jesus's gift of eternal resurrected life.
The instruction to sin no more is therefore roughly equivalent to Jesus urging people to accept the gift of resurrected life eternal, through believing and following Him.
"Sin no more" actually means therefore - as we might say it - "convert to Christianity".
In Chapter 6 Jesus varies the symbol, somewhat:
[The people said:] Our fathers did eat manna in the desert; as it is written, He gave them bread from heaven to eat....
[Jesus replied:] Moses gave you not that bread from heaven; but my Father giveth you the true bread from heaven. For the bread of God is he which cometh down from heaven, and giveth life unto the world.
Then said they unto him, Lord, evermore give us this bread.
And Jesus said unto them, I am the bread of life: he that cometh to me shall never hunger; and he that believeth on me shall never thirst.
Again the contrast is between the only temporarily-satisfying "bread" of this world, and the eternally-satisfying bread from heaven after-which we will never hunger (and also the drink which permanently abolishes thirst, presumably "living water") - that shall be given - after death - to those who "come to" Jesus.
Chapter 7: In the last day, that great day of the feast, Jesus stood and cried, saying, If any man thirst, let him come unto me, and drink. He that believeth on me, as the scripture hath said, out of his belly shall flow rivers of living water.
Here there is again implicit the earlier idea (from Jacob's well) the idea of ordinary water versus "living" water - to mean resurrected life everlasting. The man who thirsts is one who desires eternal life in the Kingdom of God.
And the path to that life leads through death via "believing-on" Jesus - implying "belief" entails trusting and following the person of Jesus, at, and after, our death.
Other similar passages can be cited, where contrast is drawn between, on the one hand, this-worldly and temporary ameliorations (such as Moses's provision of manna); and, on the other hand, the eternal and transformative life-beyond-life that Jesus brings and offers.
It seems to me that there is a pattern through the Fourth Gospel of Jesus repeatedly denying that His business is to offer what we might term secular improvements - e.g psychological and sociopolitical benefits; and instead many attempts to explain (with various 'analogies', or symbols) that his message is not about this, but about the next, world.
Now, of course, belief-in and desire-to-accept, Jesus's offer of eternal resurrected life in the Kingdom of God is almost certain to have effects on this mortal life... But any such effects on this-life are secondary to expectation of the-life-to-come.
This is worth emphasizing, because I think many or most Christian get it the wrong way around - and thereby fall into the error Jesus strove so often to correct. They assume that Christianity is about doing particular stuff in this world in order to get to the next world.
Indeed, some Christians put so much emphasis on the particular stuff that must be done in this world; that they hardly ever even think-about the next world.
Some even ignore the primary promise of Heaven; and instead focus almost-exclusively on the quadruple-negative life purpose; of not-doing stuff that must be eschewed, in order to avoid-Hell!
But Christianity is primarily about resurrected life after and beyond this mortal life; therefore, the effects of Christian belief on this mortal life are secondary to, contingent upon, the anticipated fact of resurrection in a mortal life.
Effects of Christian belief on this mortal life are thus a secondary consequence of the expectation of eternal life.
Any changed behaviours ought-to derive from the different perspective on this-life that results from belief in the life-to-come.
Note: Then there is a long-running disputation about whether we can, or should, be confident about the life-to-come - i.e. "salvation".
Many Christians have believed that salvation is difficult, complex, rare, only possible via a church and its requirements...
But that is not what comes across in the Fourth Gospel. In the Fourth Gospel; it seems that salvation is something like a decision and a commitment; and that those who have chosen salvation (by means of following Jesus) ought to be confident of salvation (so long as they continue to remain committed to it); and then... live their lives on the basis of this confident expectation.