In his poem "Lines Composed a Few Miles Above Tintern Abbey," what is Wordsworth saying about the cycles of life and maturity?
This is a personal, autobiographical poem. Contemplating the landscape of the Wye, Wordsworth compares his more sensual perceptions when he was younger with his more thoughtful perceptions as an older man.
Having been gone from the Wye for five years, Wordsworth notes that during that absence, he would mentally return to the scene for "tranquil restoration" during "hours of weariness." Wordsworth returns to the Wye to experience its nature again. He believes that, like his experience five years prior, this new experience at the Wye will give him present and future joy:
Of present pleasure, but with pleasing thoughts
That in this moment there is life and food
For future years.
From lines 65-111, Wordsworth describes the transition from his youthful experiences with nature to his more thoughtful perceptions later in life. When he was younger, he experienced nature primarily through the senses, somewhat passively:
Their colours and their forms, where then to me
An appetite; a feeling and a love,
That had no need of a remoter charm,
As he grew older, Wordsworth could no longer experience nature in this purely physical and reactive way, as if it were brand new. He regrets the loss of this kind of experience. But he believes that, in his maturity, his more philosophical interaction with nature has made up for that loss:
Faint I, nor mourn nor murmur; other gifts
Have followed; for such loss, I would believe,
As an older man, his contemplation of nature (and its use to him as a transcendent "tranquil restoration" in the present or in memory) is "more deeply interfused." In fact, he is no longer experiences things in a passive way; combining the ideas of artistic creation and perception as being partly passive and partly creative, his experience with nature is more active and philosophical.
In the last section of the poem, Wordsworth hopes his sister, Dorothy, will have the same reaction to nature as she grows older; that she, more thoughtful as she ages, will use these memories "as a dwelling-place / For all sweet sounds and harmonies;" notably in times of pain or grief.
The general meaning is that while Wordsworth misses the wild, thoughtless experiences of his youth, he appreciates his more thoughtful and therefore more meaningful perspective about life and nature as he matures.