The speaker looks back on childhood and describes himself as a daydreamer, though in an oddly roundabout way. "What my mind was / I did not sing" suggests he never put his inner life into words or song. It stayed private, unspoken, maybe even a little puzzling to him.
The middle lines are the most vivid. The boy "would turn the morning off," as if the real, ordinary day were a switch he could flip, so he could get on with "making tomorrow anew." That phrase suggests a mind always busy imagining what comes next, more at home in the future than the present.
The last two lines feel like a glimpse of where that imagining went: a sail, a coast, a god. The images are open and a bit mysterious, pointing toward distance and wonder rather than anything concrete. The mood is quiet and wistful, with a sense of looking back at a restless, dreaming self who was always drifting somewhere else.