I would say a combination of both, that is looking forward. If you keep walking and looking up at the sky you could well bump into a pole or wall. If you look only at the ground the same would apply. But I think the inference here is: should we look up to better things spiritually, or go with the practical and pragmatic?
Once again, it would be better to have a combination of both, which amounts to looking forward and seeing where we are going, but at the same time being aware of where we are at moment and where we're liable to place our feet.
It is said that a human soul is made up of body, mind and spirit. The spirit is the Observer, the eternal us. The mind and body are our servants, or should be if we're to be able to look ahead and yet be aware where we are at the moment.
So should we look at the sky or the ground as we travel through life? The answer is both.