Step 1: Poet's Positive Emotions.
The poet views a thing of beauty as a source of eternal joy. He feels that its beauty remains forever, growing more profound with time. It is something that provides perpetual happiness and satisfaction.
Step 2: Everlasting Joy.
According to the poet, a thing of beauty gives lasting pleasure. Its appeal does not fade with time, but instead continues to grow, providing joy that never diminishes.
Step 3: Conclusion.
The poet's feelings about beauty are filled with reverence and admiration, seeing it as an everlasting source of peace and happiness.
Final Answer: \[ \boxed{\text{The poet sees a thing of beauty as a perpetual source of joy that never fades. It continues to increase in loveliness, offering lasting peace and happiness.}} \]