As you write in your question, one of the themes of Wordsworth's "Lines Composed a Few Miles above Tintern Abbey" is that nature has the power to heal and nurture the human spirit.

The poem begins with the narrator looking at a beautiful rural landscape.  Among the images he sees are:

*"steep and lofty cliffs"

*"dark sycamore [trees]...
plots of cottage ground...orchard tufts,
Which at this season, with their unripe fruits,
Are clad in one green hue, and lose themselves
'Mid groves and copses"

*hedgerows, hardly hedgerows, little lines
Of sportive wood run wild; these pastoral farms,
Green to the very door"

In the second stanza, the narrator describes how he has often used the memories of this scene to heal his soul:

oft, in lonely rooms, and 'mid the din
Of towns and cities, I have owed to them,
In hours of weariness, sensations sweet,
Felt in the blood, and felt along the heart;
And passing even into my purer mind,
With tranquil restoration

To paraphrase:

Often, when I was in a lonely room, exhausted, and amidst the noise of a town or city, I have thought of this scene and it has brought me sweet feelings of quiet healing; these feelings I felt in my blood and in my heart.