The poem
Look not in my eyes, for fear Thy mirror true the sight I see, And there you find your face too clear And love it and be lost like me. One the long nights through must lie Spent in star-defeated sighs, But why should you as well as I Perish? gaze not in my eyes.
A Grecian lad, as I hear tell, One that many loved in vain, Looked into a forest well And never looked away again. There, when the turf in springtime flowers, With downward eye and gazes sad, Stands amid the glancing showers A jonquil, not a Grecian lad.

Look not in my eyes, for fear
In the first stanza, the poet is warning beloved not to look into his eyes for in his eyes, beloved will see his own reflection and will fell in love with the face, same the way poet has fallen in love with the same face. and after falling in love, he has faced lots of pain and he is warning beloved of all those pains.
second stanza is the story of a person who fell in love with his own reflection and became so absorbed that he turned into a flower: Jonquil.
Theme: Sometimes, people get so much involved in love that they forget their existence.
Situation: The pains poet faced in love made him write the poem.
Speaker: the speaker is a wounded lover who faced a lot of pains in love