In the poem's fourth stanza, the speaker recalls his feelings of youthful innocence. He acknowledges that he is a long way removed from the boy who "bounded o'er the mountains" and who seemed to be running away from something rather than through a landscape he revered. He recognizes that his youthful passions have been extinguished, but he does not mourn them. The wisdom and experience that supplanted them are "abundant recompense."

The speaker goes on to say that although he does not experience nature exactly as he did as an innocent youth, its value remained with him. It has deepened and shaped the man he became. It has sustained him when he dwelled in urban settings and helped keep him grounded. His return to this natural setting five years after leaving it sparks a deeper and even more sacred appreciation that he knows will last the rest of his life.

In the next stanza, watching his sister revel in the natural world, the speaker is gratified to know that she, too, will remember and be shaped by the majesty of nature. It is a bond that they will share because she will also ultimately leave innocence behind as he did. He hopes that she will be forever sustained by what she experienced then as he is now.

In "Tintern Abbey", Wordsworth is pretty stoical about the loss of innocence. He sees it as regrettable, but also as a necessary part of growing up. When Wordsworth returns to this awe-inspiring natural landscape after many years' absence, he reflects on the same things as in his youth. The difference, however, is crucial; for now he is more mature and therefore able to reflect more deeply on the world around him and his relation to it.

Once lost, innocence cannot be regained. Among other things, this means that the place that Wordsworth visits in the poem doesn't effect him quite the same way it did five years previously. But that's not really a problem because his changed perspective on things allows the poet to gain access to life in a deeper, more philosophical way. And this is a source of considerable joy.

In this poem, the speaker revisits a place of great natural beauty that has been incredibly important to him. However, as he revisits it, he finds that his feelings about it and his awareness of what it represents to him have changed greatly as a result of the intervening years and the way that he has matured as a result. Although he recognises that he has now lost some of the first youthful excitement that he had when he visited Tintern Abbey as a young man, he does not regret this loss of innocence, because he believes that this loss has been more than balanced by the gaining of a maturer outlook on life and a deeper relationship with nature:

For I have learned
To look on nature, not as in the hour
Of thoughtless youth; but hearing oftentimes
The still, sad music of humanity,
Nor harsh nor grating, though of ample power
To chasten and subdue.

The speaker has seen that perhaps his view of nature and the joyful innocence it portrayed was not necessarily the most accurate view of the natural world that he could have formed. Now that he is older and more mature, he is able to reflect on the way in which his relationship with nature is inextricably intertwined with the "still, sad music of humanity" that gives him a more sober outlook and understanding of life. Wordsworth is able to appreciate his new insights as being something that forms a worthy exchange for his innocent outlook that he has lost.