The speaker is a drifter, someone who moves from place to place without settling, and the poem catches what that life feels like from the inside. The places he passes through are "made of bridges and old differences," a strange and compact phrase. Bridges suggest crossing and not staying, while "old differences" hints at the gaps between him and the people or towns he meets. He doesn't seem to take in these places while he's there. He only remembers them "afterwards," as if they come into focus once he has already left.
The second stanza is blunt and bare. He says he has no friends "but sleep / and the morning sand." Sleep is his comfort and escape, and the sand suggests he beds down outdoors, perhaps by a river or shore. The mood is quiet, lonely, and a little weary, but not self-pitying. He states his situation plainly, almost with acceptance, and the spare language leaves the reader to feel the emptiness around him.