Four short lines, and they work almost like an instruction the speaker gives to themselves. "Think" is the first word, a command, and the title, "Concentration," suggests the kind of focus needed to settle a restless mind. What the speaker asks for is strange and physical: let blood "go to ink." The body's lifeblood turns into the stuff of writing, so thinking and writing become one act, something felt in the veins rather than only in the head.
Then the poem shifts outward. Ivy, in the evening, seems to "sing" the house to bed, as if the plant were a lullaby-giver. The house is treated like a living thing, or a child, being soothed toward sleep. The word "our" hints at a shared home, though the poem doesn't say who else is there.
The mood is hushed, drowsy and tender. Effort and calm sit side by side: the speaker concentrates, and the evening quietly settles around them.