Oh, I have made myself a tribe out of my true affections, and my tribe is scattered! (17-19)
The speaker has lived, loved, and lost over the course of his existence and sometimes that can be emotional. He seems to lament the fact that he no longer has those attachments. Growing is a good thing, but it's not always easy to leave people and places behind.
How shall the heart be reconciled to its feast of losses? (20-21)
The speaker is disheartened and at his lowest point, recalling all the connections he has lost. He expresses this heartache by asking a rhetorical question. It's rhetorical because there's no definitive answer and he's essentially asking himself. It's hard to think clearly when emotions are involved, but as the later lines in the poem suggest, he seems to find his answer.
when the moon was covered and I roamed through wreckage, (33-34)
The speaker recalls being lost and alone in a harsh environment. The use of the word "wreckage" is an interesting choice here. Perhaps it's offering some grounding and foreshadowing for another interesting word, "litter," that appears in line 38.