Similarly lost in meaning is Frost's "Stopping by Woods on a Snowy Evening" which is a beautiful poem, but many people don't see the suicidal undertone. I've had it memorized for years and only just learned about this.
While in high-school English class taking an exam, in a fit of boredom (having completed it early) I scrawled the Hamlet soliloquy "To be or not to be" (going on for several lines) in the margin. Next morning, the teacher took me aside and asked as gently & tactfully as possible if everything was OK. Momentarily puzzled (yes, everything was fine), the meaning of Hamlet's mutterings suddenly hit me: the lines were not just a vague pontification about life, he was actually contemplating suicide. I assured the concerned teacher everything really was OK.
The woods are lovely, dark, and deep, But I have promises to keep, And miles to go before I sleep, And miles to go before I sleep.
The narrator has been traveling far to fulfill the promises he made to others. He's looking at the lovely, dark, deep woods and thinking how peaceful they are. The woods are a metaphor for death, which is dark and lovely because you don't have to worry about life's hardships. The miles are not distance, but a metaphor for time. The narrator decides he has to continue on, because he cannot sleep/die before fulfilling his promises to those he made them to.
Frost was an amazing writer whose poems beautifully described rural settings. But I think because of his brilliance, it is likely that his poems had deeper meaning than their face-value imagery. But it's also possible that they were one-dimensional, I just doubt it.
Lovely - All your worries and obligations no longer exist
Dark - When we imagine the absence of life it's like the absence of light, darkness
Deep - Death is deep because it's irreversible and never-ending