Today, the third of Tammuz, marks the twenty-third anniversary of the death of my teacher, mentor and guiding light: Rabbi Menachem Mendel Schneerson, known to us simply as “the Rebbe.”Every year, this day takes its toll. I miss the Rebbe dearly, and yearn to hear his voice again. His was a voice that shone with confidence, sparkled with love and shimmered with its steadfast promises of hope.It was that last theme, though, which in my mind represents the central pillar of the Rebbe’s eternal message.That mankind, despite the horrors and confusions of his world, still had what to hope for. The Rebbe dedicated his life, and the lives of all those drawn into his mission, to perfecting the world and bringing about the Messianic age, where “men would beat their swords into plowshares and... no longer learn the art of war.” God’s light, the Rebbe promised, would soon shine so brightly that all the world’s moral failings and doleful defects would simply disappear amid its glow.The Rebbe inherited the mantle of leadership just five years after the Holocaust and mankind’s greatest war.During the 44 years of his leadership, the world would experience eight more genocides and dozens of wars. Five of the latter would be visited upon the State of Israel, and countless terrorist attacks would be perpetrated against its citizens. Jews disappeared through assimilation at record rates as our millennia-old traditions approached ever closer to a record recession. On all fronts, it seemed, the Jewish People and their world were deteriorating, and hope seemed to grow ever more distant with every passing year.The Rebbe, however, refused to see it that way. He found in every event another reason to believe that God would soon redeem the earth and perfect it for all His children. When the UN was founded, the Rebbe saw in it the realization of Isaiah’s prophesies that nations would soon band together in pursuit of peace over power. When Israel faced increasingly dire threats, the Rebbe promised (presciently, indeed) that the Jewish state would see stunning victories since God was slowly easing himself into the world, thereby forcing evil into decline. When Israel actually achieved those victories, the Rebbe proclaimed that these were in fact miracles heralding our ascent into a better time.And if the Jewish people were becoming increasingly illiterate in their faith, the Rebbe saw in it only a responsibility and opportunity to bring them back with acts of loving-kindness, thereby proving the deepest possible link all men possessed with their Creator – a link so strong that it would serve as the ultimate testament to the fact that we had finally earned God’s promises of a perfect world. So deeply did the Rebbe believe that we would march together into the Messianic age, where “death will be swallowed forever,” that he refused to appoint a successor. The Rebbe hoped to a point where he could not fathom failure. With the Rebbe, there would be no Plan B.The Rebbe, in short, refused to see the darkness, opting instead to focus on the inevitable sunshine that belies all shadow. And, in so doing, the Rebbe lit up our world.Today, I could really use that light.I’m currently writing from Berlin, where I’ve come to see firsthand the sites where Hitler planned his Final Solution and set it into its monstrous motion.I find even a passing thought of the Holocaust to be, on a certain level, paralyzing. As I actually wandered the halls of a white mansion in the Berlin suburb of Wansee where, just 75 years ago, German officials sipped champagne, smoked cigars and planned the mass extermination of six million of my Jewish brethren – the disintegration of hope seems complete. As I walked out of the elegant Berlin villa, the world had taken on a darker shade.I find today that I must latch on to the Rebbe and the hope he represented more than ever before.The Holocaust, to me, does not just represent the brutality of the Nazis, but rather stands as a damning testament to the brokenness of our world. As children died of starvation in their mothers’ arms, as men were shot by firing squads in front of their families, as women and children were herded into the gas chambers – where was God? Where was his strident hand of justice, which promises to visit doom upon evil men? Where was his ringing voice of righteousness, which proclaimed the sanctity of human life? Where was his warming caress of compassion, which promised us comfort in times of sorrow? God, and the hope he represented in our world, seems to have dissipated along with the bodies of millions of innocent Jews into the clouds of smoke that plumed above the camps which I have come to visit. Today, too, my inclination toward cynicism drives forth on an abundance of fuel. On the world stage, crematoria are still churning out smoke in Syria, and hundreds of thousands remain helpless at the hands of the butcher of Damascus, Bashar Assad. Iranian mullahs continue to call for the wholesale slaughter and destruction of my people in the Jewish State. Hundreds of thousands of rockets remain dug into position, poised to strike innocent Israeli families from Lebanon and Gaza.On a domestic level too, brokenness is everywhere.Families across America are failing; divorce is at an all time high. My fellow Americans feel increasingly fractured at their source, with millions now turning to opioids and other drugs in the hope that something might just serve to numb the pain. How can I, in this misery, still cling to hope? And that’s when I remember my Rebbe. When I was a boy the Rebbe responded to a letter I had written expressing the deep pain I felt since my parents’ divorce. I gave him that letter in a private audience. The Rebbe blessed me. Rather than wallow in my own darkness, he demanded that I become a light to my family, my school, my people, and the entire world instead. In those words, however, I found not just a blessing, but a mission – one defined by action over mulling, and confidence over despair.And so, as I walk among the remains of the Nazi regime and the concentration camps they built in their mad program of murder. I refuse to lose sight of my mission and its foremost objective: that I act in whichever way I can to bring light into this jaded world.It’s not a mission I alone can complete. Nor so is it a goal that I believe mankind can achieve as a whole. But God can. And as the Jewish sages instructed us: “It is not incumbent upon you to finish the work, but neither are you free to exempt yourself entirely.”We need only do what we can. God will do all the rest.This year, let us all re-commit to the hope and action that defined the Rebbe’s legacy. Let us not be beaten down by the enormity of this task, but march forth astutely, with confidence in our power as people to inch toward a perfect world.With people, families and entire nations so deeply mired in turmoil, there is simply no Plan B.The author, “America’s rabbi,” whom The Washington Post calls “the most famous rabbi in America,” is the international bestselling author of 30 books including his most recent The Israel Warrior. Follow him on Twitter @RabbiShmuley.