Read the excerpt from "Mending Wall." Spring is the mischief in me, and I wonder If I could put a notion in his head: “Why do they make good neighbours? Isn’t it Where there are cows? But here there are no cows. Before I built a wall I’d ask to know What I was walling in or walling out, And to whom I was like to give offence. Something there is that doesn’t love a wall, That wants it down.” I could say “Elves” to him, But it’s not elves exactly, and I’d rather He said it for himself. What is the speaker’s mood in this excerpt? unhappy playful childish determined