"...Out of the fire there spoke a commanding voice."
"Begone and trouble me no more! If you touch me ever again, you shall be cast yourself into the Fire of Doom."

“If someone tells you what a story is about, they are probably right.
If they tell you that that is all a story is about, they are very definitely wrong.”

Neil Gaiman - introduction to Farenheit 451, by Ray Bradbury

Smeagol/Gollum was never a nice guy, but after some five-hundred years he had been totally and completely (very rare exceptions) despoiled and corrupted by “his precious”. After the robbery of his treasured Ring by bad Baggins his entire existence was focused solely on regaining the only thing that he ever loved. And when he finally regains possession, after seventy-eight years, his ecstasy is boundless and he heedlessly, with no thought of personal safety, jumps for joy on the edge of the Cracks of Doom, trips or slips and falls into the fire with a last word – “precious”. We might equate his reckless joy and subsequent death to something akin to the overwhelming reappearance of a deceased mother, where the mind would understandably take a temporary holiday.
So, the “motive force” is simply the reckless heedless mind of Gollum

Bracegirdle

It occurs to me that (as Sam perceives in the vision he is given) Frodo has seemingly been spiritually purified by his ordeal, in every way save his enslavement to the Ring. If so, then his curse on the slopes was still partly in his own name as well as in the name of the Ring. That might explain how the Ring's curse led to the Ring's own destruction: it was issued through a hobbit who, with the ring of fire at his chest, was otherwise wearing a white robe. The former doomed Gollum - the latter doomed the Ring.

squire

And we can debate forever WHY he [i.e. Gollum] died. It sure seems like an accident, but we have Frodo's strong curse and Faramir's feebler curse to give us pause, plus there's just plain fate involved in all of this. If Frodo was *meant* by a higher power to be the Ring-bearer, did that same higher power give Gollum a nudge? Or did irony kill Gollum, as in the old expression "be careful what you wish for"? Or maybe morality killed him, since he was too careless in his victory. Or did the Ring, ever treacherous to any owner but Sauron, make Gollum fall, and given that the Ring wasn't all that smart, it didn't realize it doomed itself? Is this another example of "oft evil will shall evil mar"? Oh, it's fun to think about these things!

Curious G

The Ring's ambiguity is present almost the first time we see it, in 'The Shadow of the Past', when Gandalf tells Frodo, 'Give me the ring for a moment'. Frodo unfastened it from its chain and, 'handed it slowly to the wizard. It felt suddenly very heavy, as if either it or Frodo himself was in some way reluctant for Gandalf to touch it.
Either it or Frodo.... The difference is the difference between the world views I have labelled above as 'Boethian' and 'Manichaean'. If Bothius is right, then evil is internal, caused by human sin and weakness and alienation from God; in this case the Ring feels heavy because Frodo (already in the very first stages of addiction, we may say) is unconsciously reluctant to part with it. If there is some truth in the Manichaean view, though, then evil is a force from outside which has in some way been able to make the non-sentient Ring itself evil; so it is indeed the Ring, obeying the will of its master, which does not want to be identified.Both views are furthermore perfectly convincing. ...The idea that on the one hand the Ring is a sort of psychic amplifier , magnifying the unconscious fears or selfishnesses of its owners, and on the other that it is a sentient creature with urges and powers of its own, are both present from the beginning..."

Prof. Tom Shippey's Book "JRR Tolkien, author of the century." (my bolds)

You cannot press the One Ring too hard, for it is of course a mythical feature, even though the world of the tales is conceived in more or less historical terms. The Ring of Sauron is only one of the various mythical treatments of the placing of one's life, or power, in some external object, which is thus exposed to capture or destruction with disastrous results to oneself.

Tolkien Letters 211 (my bolds, emphasising what I see as the point of comparison)

"But to achieve this he had been obliged to let a great part of his own inherent power (a frequent and very significant motive in myth and fairy-story) pass into the One Ring. While he wore it, his power on earth was actually enhanced. But even if he did not wear it, that power existed and was in ‘rapport’ with himself: he was not ‘diminished’. Unless some other seized it and became possessed of it. If that happened, the new possessor could (if sufficiently strong and heroic by nature) challenge Sauron, become master of all that he had learned or done since the making of the One Ring, and so overthrow him and usurp his place. This was the essential weakness he had introduced into his situation in his effort (largely unsuccessful) to enslave the Elves, and in his desire to establish a control over the minds and wills of his servants. There was another weakness: if the One Ring was actually unmade, annihilated, then its power would be dissolved, Sauron’s own being would be diminished to vanishing point, and he would be reduced to a shadow, a mere memory of malicious will. But that he never contemplated nor feared. The Ring was unbreakable by any smithcraft less than his own. It was indissoluble in any fire, save the undying subterranean fire where it was made –and that was unapproachable, in Mordor. Also so great was the Ring’s power of lust, that anyone who used it became mastered by it; it was beyond the strength of any will (even his own) to injure it, cast it away, or neglect it. So he thought. It was in any case on his finger."

Tolkien Letters 131

"Begone and trouble me no more! If you touch me ever again, you shall be cast yourself into the Fire of Doom."

'You, he, she, it' or 'they shall' expresses intention or determination on the part of the speaker or someone other than the actual subject of the verb, especially a promise made by the speaker to or about the subject

Fowler's Modern English Usage 3e, Oxford 1996

The chief modification of that general rule is the survival of the original (the Old English) senses of shall and will. Dr Onions summmarizes thus: 'Shall denoting obligation, necessity or permission; will denoting resolve or willingness'

Usage and Abusage, Eric Partridge - originally published 1942- 1947 : I have the new edition 1994, but there's no reason to suppose that this passage - about a distinction that has become pretty historical even in english-English usage - has been changed since the 1940s

Fowler's view in short amounts to this: that if anyone has been brought up among those who use the right idiom, he has no need of instruction; if he has not, he is incapable of being instructed, because any guidance that is short and clear will mislead him and any that is full and accurate will be incomprehensible to him

Every English text-book will be found to begin by stating the rule that to express the 'plain' futureshall is used in the first person and will in the second and third
I shall go
You will go
He will go

and that if it is a matter not of plain future but of volition, permission or obligation it is the other way round:
I will go (I am determined to go, or I intend to go)
You shall go (You must go, or you are permitted to go)
He shall go (He must go, or he is permitted to go)

But the idiom of the Celts is different. They have never recognised 'I shall go'. For them 'I will go' is the plain future. The story is a very old one of the drowning Scot who was misunderstood by English onlookers and left to his fate because he cried, 'I will drown and nobody shall save me'.
American practice follows the Celtic, and in this matter, as in so many others, the English have taken to imitating the American

The Complete Plain Words by Sir Ernest Gowers, Revised by Sir Bruce Fraser, HMSO 1973
(This quoted text is, however, Gowers' unrevised wording from the earlier 1952 edition (initially circulated as a Government style manual from 1948. Fraser has recused himself from this passage with a footnote that perhaps shows the regional snobbery of all this: 'I have assumed that since I am a Scot nothing I may say about [this] is likely to command any respect south of the Cheviots'.

...In the last need, Sméagol, I should put on the Precious; and the Precious mastered you long ago. If I, wearing it, were to command you, you would obey, even if it were to leap from a precipice or to cast yourself into the fire. And such would be my command. So have a care, Sméagol..!

For a moment it appeared to Sam that his master had grown and Gollum had shrunk: a tall stern shadow, a mighty lord who hid his brightness in grey cloud, and at his feet a little whining dog. Yet the two were in some way akin and not alien: they could reach one another's minds.

...do you remember Gandalf's words: Even Gollum may have something yet to do? But for him, Sam, I could not have destroyed the Ring. The Quest would have been in vain, even at the bitter end. So let us forgive him! For the Quest is achieved and now all is over.