What does the expression "I sate reclined" indicate about the poet's state of mind in "Lines Written in Early Spring"?

The second line of the poem indicates that the speaker is in a relaxed state of mind. And why not? He's sitting in a grove enjoying the beautiful sights and sounds of nature. The speaker feels a sense of oneness with the natural world, a deep connection that makes him a part of nature every bit as much as the primrose tufts, the periwinkles, and the budding twigs which bring him so much joy.
But the speaker's tranquil state of mind doesn't last for very long. Because soon he is troubled by sad thoughts. He muses on the realization that though the human soul is closely linked to all the joyous wonders of nature, the relationship between man and man is very different, and not in a good way. The implication is that the harmony that prevails in nature and which characterizes the connection between the natural world and the human soul is notable by its absence from relations between human beings, which, more often than not, are mutually antagonistic.
https://www.poetryfoundation.org/poems/51001/lines-written-in-early-spring