With the world looking dangerous again, let's remember the optimism of Berlin in 1989 Closer to home here in Europe, borders are being changed by force for the first time since World War II, after Russia's illegal annexation of Crimea and involvement in the destabilising events in Eastern Ukraine. In Africa, the world is waking up to the great risk posed by the Ebola outbreak. Although the European economy is starting to turn a corner, growth remains feeble and unemployment unacceptably high. The fear of falling living standards has driven an increasing number of European citizens into the arms of populists. READ MORE Fall of the Berlin Wall: The guard who opened the gate - and made history In times like these, we can draw hope and inspiration from the events of 9 November 1989. Indeed, many Germans still consider the fall of the Berlin Wall 25 years ago nothing short of a miracle. Through the peaceful uprising of thousands of dissidents and demonstrators, an era of senseless division ended. After decades of cruel separation, families in East Germany were finally reunited with their relatives in the West. A world torn by the misery of confrontation and the Cold War took an enormous turn for the better. What lessons should we draw from the remarkable events of 25 years ago? The first is the importance of optimism. In January 1989, the leader of East Germany Erich Honecker predicted the wall would remain in place for 50 or 100 more years. However, thanks to the courage of the activists who braved warnings from the state authorities in Leipzig and other cities in East Germany, the fall of communism came more quickly than anybody expected. On 23 October 1989, more than 300,000 protesters gathered in Leipzig to demonstrate for unity. We must also thank the governments of Hungary and the then Czechoslovakia who defied the threat of Soviet reprisals to allow East Germans safe passage to the West. The second lesson is the need to tear down borders - physical and mental. The defining chant of this historic night remains: "We are one people." Putting decades of separation behind them, Germans from East and West came together on 9 November 1989 to celebrate the first step towards freedom. As thousands of East Germans started crossing the checkpoints to West Berlin under the helpless gaze of the border guards, the citizens of West Berlin awaited them with flowers and champagne. The most defining pictures of this night remain the young Germans from both sides who climbed the top of the wall to celebrate their reunification. Ever since these events it has been Germany's long-term goal to extend this freedom to our Eastern neighbours and partners within the European Union. The debate on immigration should not distract us from the fact that the enlargement of the EU has been a major success. As Germans, we know the value of removing barriers for people, goods and thoughts. Only by granting new member states from Eastern Europe quick accession to the EU did we manage to repair the damage done by communism. When the world looks dangerous again, we can find hope and inspiration in what happened 25 years ago. Freedom and democracy - and a unified strong Europe - are still powerful ideas for the 21st century. READ MORE A partnership between China and Europe is needed to tackle climate change