What is Reformed Theology/Calvinism 16: Sovereignty & Evangelism, Prayer, & Missions

If God is sovereign over all things & He elects people to salvation then why do we still evangelize? Why do we pray? Why do we send missionaries? Are people lost because of our failure to evangelize or pray? What are the practical implications of Calvinism? How does it effect our personal holiness? Does the right understanding of the doctrines of grace & who God is effect our spiritual maturity?