Really nice poem about a broken past that "can't be fixed"
The speaker seems go be closed off as they've "build a house with brittle bricks" with an unstable "base" indicating a metaphorical danger if one tries to enter their inner world, "you'll risk your life if you come in".
It appears that this past is one of a broken "[friendhsip]" where the speaker informs us that their bond was not healthy or stable much like the house itself. In an unhealthy viewpoint, the speaker argues that "I ran out of stable materials", "to keep you here, to keep you near". Metaphorically speaking, we can understand how the speaker initially had an intention of creating a very strong relationship with their friend and one which will last for a long period of time, like a house, as seen also from the repetition. It shows persistence.
What we understand in the final stanza is how this "beset" was caused by "secrets". Since the speaker argues that "you wouldn't be upset", we can argue that they were really insecure in the past hiding away what troubles them and ensuring a closeness. With that said, in this case, I will say that the speaker might've become clingy to that person in the laster events of the last. Hence now for confessing their "sin" there is no more confusion and allows the friend to "forget" them since they'd be released to know the answer. This is my interpretation.
The structure of the poem is free verse as you do in modern poetry. Each stanza seems to enlarge which can connote a various amount of ideas. It could be the speaker's insecurity rising up to the surface from its hidden place or even the distance between the friend and the speaker becoming farther and farther.
There's no enjambment or caesura however many of the lines are complete meaning that the speaker wants to express their emotion and regret and clearly as possible. They also attempt to project the closeness they once felt woth their friend through the couplets used.
Overall, this is really nice