Six short lines, no capitals, no punctuation, and the reader is already falling. "falling all night on me" starts mid-motion with a participle that has lost its subject. What is falling? Rain, darkness, sleeplessness, or the "bridge to morning" itself, which may be coming down on the speaker? The grammar won't settle, and the uncertainty is part of the effect. Night here is not a calm interval but a weight that happens to you. The poem never says "insomnia", but "all night" and the pull toward morning suggest someone awake and waiting to be carried across to daylight. That is an inference, though a natural one.
The title sets a folk-tale scene: a bridge, a crossing, a troll in the way. If the old story of the goats who trick the troll is in the background, and the title makes that likely, then the troll is a creature who gets beaten by a fib. The smallest goat promises that a bigger brother is coming. The poem keeps that link between trolls, bridges and deception and turns it inward. The troll is no longer under the bridge but inside the speaker: "heart childish as a troll". The simile surprises, because trolls are usually menacing and "childish" shrinks him into something petulant, territorial and easy to fool. It is a rueful self-portrait, a heart that guards its small patch and sulks.
The second couplet gives that heart a home: "in a paper palace". "Palace" promises grandeur and "paper" cancels it. The p sounds even rustle a little, as if the line were made of the material it names. A paper palace is built for play or show, and it cannot survive weather or a strong breath. It is also a different kind of place from the dark under a bridge. This troll has dressed up his hiding place, as people do when they give their fears a more dignified shape.
Only the final couplet has a main verb, so the poem moves from two fragments to a single claim: "a lie is as much to build with / as to laugh down". The balance of "as much… as" makes the lie neutral raw material, equally good for construction and demolition. The paper palace is presumably built of such lies, the stories we tell to feel safe or important. The poem adds that the same stories can be taken apart by laughter. "Laugh down" is an unusual phrase. It suggests ridicule strong enough to topple a wall, as if a joke were a battering ram. The tone is wry, not solemn. The speaker admits to building the palace and also expects to bring it down himself.
The line lengths help the collapse. The lines run at about six syllables, swell to eight in "a lie is as much to build with", then shrink to four in "as to laugh down". The line break after "with" leaves a preposition hanging, so we lean forward, and then the short last line drops. Its final word, "down", answers the "falling" of the opening and closes a circle from the first line to the last.
There is no rhyme, but the sound is carefully patterned. The l of "falling", "all", "troll", "palace", "lie" and "laugh" runs through the poem like a thread. "Bridge" in the first couplet is picked up by "build" in the last, and the short i of "bridge", "childish", "in", "build" and "with" keeps the diction small and close. The vocabulary is plain and nearly childlike, which suits a poem about a childish heart.
What makes the poem worth reading is how much it holds in so little room: a sleepless night, a fairy-tale image, a self-portrait and a small philosophy of fiction. It doesn't scold the speaker for self-deception, and it doesn't excuse it either. It treats lies as both shelter and joke. The "bridge to morning" in the first line may be one of these constructions, a story told to get across the dark. If so, the poem asks whether we can cross on something we know could be laughed down, and it leaves that unanswered.