Okay, here is a quick answer. The poem reminded me of how I myself have often felt living in a big city and being subjected to all the stress that goes with such an environment. It reminded me of the urges I have felt to escape from the cold, gray, overcrowded, competitive environment and to go off to someplace like that lake isle where I could live a simple life and be free. I was reminded of Henry David Thoreau's Walden. He lived a simple life and communed with nature. Many people love that book because they can identify with him. I suspect that Yeats was inspired by reading Thoreau. E. B. White, who wrote for the New Yorker for many years, found that he couldn't stand Manhattan and moved to a farm in Maine, where he wrote Charlotte's Web and Stuart Little, among other things. Buddha gave up the life of a prince in a royal palace and lived the simplest possible life, as recorded in Herman Hesse's Siddhartha and elsewhere. It is not impossible to escape from the rat race, but it is extremely difficult. I understood that Yeats was not writing about how he was living on his lake isle, or how he planned to live when he got there, but how he wished he could live such a life. I understood exactly how Yeats was feeling when he composed his poem because I have felt the same way so many times myself. I also recommend the lesser known memoir by George Gissing titled The Private Papers of Henry Ryecroft.