I believe it is lonely because one of the line says "I took the one less traveled by," and I can see it sounds like the narrator is feeling lonely.
"slipped the surly bonds of earth to touch the face of God" Leaving the earth should be done against the force of gravity.
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I became, in short, the gangling farmer-boy my aunt had known, C. Scourged with chilblains and bashfulness, my hands cracked and raw from corn husking.
Scourge is something that causes suffering.</span>