It is important to change our perspectives and minds in life and not follow traditions, but how does this poem show it. Like what techniques and quotes are used to reinforce this idea? Is it the mental and imaginary barrier?
When it comes to techniques he uses to convey this notion, he compares his stubborn neighbour to "a old stone savage armed". Simile is used here.
Frost says that his neighbour uses a famous proverb of England those days, that is "Good fences make good neighbours". This statement has been reiterated in the poem in order to convince. So "Repetition" is another technique used to convey the traditional idea.
Something there is that doesn't love a wall,
The above line too is repeated. Frost implies nature and he doesn't like the wall to be mended.
Well.. Answering the first part of your question, I would say like this, It is better to change our minds not to follow useless traditions. In this poem, "Mending Walls" by Robert Frost he shows his reader how his neighbour clings to the tradition of mending a wall annually, which is, to him is totally an unwanted thing. Frost talks about human isolation here, the narrator hates the wall to be mended since there's is no use of it, because they don't have anything to seperate.
He is all pine and I am apple orchard.
My apple trees will never get across
And eat the cones under his pines, I tell him.
Before I built a wall I'd ask to know
What I was walling in or walling out,
This way the poem shows how this neighbour clings to an unwanted tradition and rejects to understand poet's explanation that this is unimportant. Frost shows his reader about the uselessness of isolating themselves by this tradition.
n each hand, like an old-stone savage armed.
He moves in darkness as it seems to me