Idealism makes room for expansion, development and innovation. Although realism helps us to be grounded with our ideas, we need first to implement idealism. We have to think with no restrictions first. Of course, as the world does not supply enough resources to satisfy our insatiable human needs and even more so with wants, our outlandish ideas cannot be put into action all at once. Idealists always see the potential in the world to be a better one, to make the lives of the future generation better than before, for evolution. And I think this is almost wholly impossible without idealism.
realism, with a bit of hope mixed in. " Hope for the bes, but plan for the worst".