NEW YORK — A forthcoming book by former NFL quarterback Tim Tebow will be a guide on how to handle success and disappointment. WaterBrook, a Christian imprint of the Crown Publishing Group, told The Associated Press that it will publish “Shaken: Discovering Your True Identity in the Midst of Life’s Storms” in October. Tebow will write about maintaining perspective “when your dreams do not go as planned.” WaterBrook also plans a companion Bible study. A former Heisman Trophy winner at the University of Florida, the 28-year-old Tebow helped lead the Denver Broncos to the playoffs in 2011 but has struggled since.