Sertorius was far from being strong enough to renew the gigantic enterprise of Hannibal. He was lost if he left Spain, where all his successes were bound up with the peculiarities of the country and the people; and even there, he was more and more compelled to renounce the offensive.
If you’ve lost focus, just sit down and be still. Take the idea and rock it to and fro. Keep some of it and throw some away, and it will renew itself. You need do no more.