The speaker is pacing, walking up and down, and the poem's first admission is that this restless motion makes him miss things. What slips by is a strange mix: love, water, and "her troubled mind." Love and water are large, elemental things that flow past whether or not anyone notices. The third item is more personal and more painful. Judging by the wording, someone close to him was struggling, and he failed to see it or respond.
The last line changes the tone. "The treaties / which made me laugh" is abrupt and slightly odd. Treaties suggest official, serious agreements, yet he laughed at them. It could be bitter humor, or a sign that he once treated important matters too lightly. The poem doesn't explain, and that gap adds to its feeling.
The mood is regretful and unsettled. Short lines mimic the walking, and the sparse wording leaves the sense of loss hanging, as if the speaker is only now recognizing what he overlooked.