This quotation comes from William Wordsworth's "Ode on Intimations of Immortality from Recollections of Early Childhood." This poem is primarily concerned with the sense of wonder we all have in childhood, which can be prompted by the simplest things in the natural world which once seemed "apparelled in celestial light" but which now we "can see no more." The primary question this poem asks is "whither is fled the visionary gleam? / Where is it now, the glory and the dream?"
The quotation you have isolated, then, is about how, from the moment we are born, we are actually moving further and further away from the understanding of God we had when "the Soul which riseth within us" was in its original "setting," in heaven. Babies come "from God, who is our home," and as we move away from childhood, the sublime which we were once able to see becomes "common" through overexposure. Childish wonder allows us to recognize the miraculous beauty of the world around us. However, Wordsworth does not wish for this to be a cause for us to "grieve"—instead, we should "find strength in what remains behind," and seek to remember that "the innocent brightness of a new-born day / Is lovely yet." The poem ends with a true expression of the Romantic Sublime, as Wordsworth states that "the meanest flower" can give him "thoughts that do often lie too deep for tears." This idea of nature prompting extremely strong feeling is one which is central to Romanticism.