I would like to point out that the Warriors of Light throughout the ages have never managed to stop a Calamity from happening. Help save people from it? Yes. Prevent it? No.

What the voice is asking us to do has never been successfully done before.

It should be noted that the previous Warriors of Light had stronger Crystals of Light then we do and most likely had a much stronger Hydaelyn helping them. In terms of the amount of power Hydaelyn can lend the Warriors of Light, we more then likely much less help then "usual". So not only must we do something no one before us has done, we have to do it with less gifted power then they had access to.