Frost uses metaphor, simile and onomatopoeia to express his emotions throughout Birches. Although there are no individual stanzas there are natural breaks in the poem which allow for a changing pace and the recognition of his emotions as he passes between the emotional difficulties of being an adult and the ability of a child to overcome hardships as, for him, they are short-lived.
Blank verse is used and Frost liked to maintain the meter of his poetry, unlike many of his peers. This created the flow - such as life itself flows. Tension is created and the disparity causes conflicting emotions:
the real world might be a place of pain, but it is also the place for love; the imaginary world is innocent, but it is also solitary and, by extension, loveless.
There is no desire throughout to change life - it must take its course- as it "bends to left and right" but the "ice storms," signifying the hard times do make Frost wistful. The "sun's warmth" on the "crystal shells" of life experience bring relief when they are "shattering and avalanching." For a time, stress is lifted.
Frost is somewhat bitter and even angry at Truth because sometimes a person needs to escape into his or her imagination - "Now am I free to be poetical?" He intimates that, otherwise, despair, as "they are dragged to the withered bracken" could take hold.
There is an admiration at the fearlessness of the boy "kicking his way down" followed by nostalgia and more wistfulness:
"So was I once myself a swinger of birches. / And so I dream of going back to be."
A reality check follows and Frost is careful to reveal that he only feels this way when he lacks direction - "the pathless wood" and feels that life is just too hard. Being able to start over would be a gift and Frost becomes hopeful and finally accepting of his lot.
The sounds increase the visual picture created as the branches "click" under the weight of adulthood but "swish " when the boy plays . The "shattering" crystal reinforces the confusion between reality and imagination.
The journey of life is to be respected, in Frost's eyes, and the ability to wish to be "a swinger of trees" is not all that bad and, if it lightens the load of responsibility , so-be-it.