Willink enlisted in the Navy SEALs after high school and rose through the ranks to become the commander of the most highly decorated special operations unit of the war in Iraq. Many books offer advice on how to overcome obstacles and reach your goals – but that advice often misses the most critical ingredient: discipline. Without discipline, there will be no real progress. I think more teens should learn his mantra: find your will, find your discipline – and you will find your freedom.