What Power does Santiago's love for Fatima give him?

I think the power to pursue his personal legend. The alchemist claims that there can be no conflict between true love and one's Personal Legend. This is because true love is defined as that love which does get in the way of the Personal Legend. In this way, the novel sets up the Personal Legend as the central organizing principle of a spiritually fulfilled life. Once the Personal Legend is identified and committed to, all other things will become clear.