Originally Posted by
cesarm
In this case, the verse you mention, doesn't constitute a known saying in Spanish. At least not one I’m familiar with, but functionally, it basically conveys the same idea as the phrase “Grass is always greener on the other side”.
Life has a certain color form afar , but once you “get there”, once you experience that moment you have fantasized so much about, it turns to be quite different to what you expected it would be.
It sort of reminds me of Lennon's "Life is what happen's when you're busy making other plans"...
So I guess in these terms your translation works perfectly fine.