If we weren't able to consider that something is possible, then we could never bring it to be--which would mean a world without art, music, writing, engineering, decor and a host of other beautiful things.
How is it we are we designed so that we can see something that isn't? Then, to begin to look for it or create it ourselves. It is a mix of vision, curiosity and creativity.
Imagination is a beautiful gift. And one worth cultivating.