One small act of courage can change your life. Small acts of courage lead to bigger acts of courage, and big acts of courage can change the world.
As someone who grew up in the 1980s, I can say this was built into our psyches. Politics and pop culture alike taught us the virtue of standing up to bullies. 
Politically, we watched as Ronald Reagan stood up the “the evil empire” of the Soviet Union. A show of strength (with a little righteous deception and some prayer meetings mixed in) helped to bring down down the communists and end the Cold War. American strength was a deterrent to our enemies and bought an extended period of relative peace. Reagan displayed courage and it paid off. Reagan’s courage not only shaped his own life and legacy, it shaped the course of modern history.
It’s striking to me that two of the most popular movies from the 1980s, "Karate Kid" and "Back to the Future," both deal with boys learning to courageously stand up to bullies in a physical way. In "Karate Kid," Daniel LaRusso wins the respect of those who had bullied him by training hard and then beating them at their own game. In "Back to the Future," there are two George McFlys, one for each of the two 1955s in the movie. There is George McFly, the loser we see at the beginning of the movie, and there is George McFly the stud we see in the alternate time line at the end. What made the difference between the two? One punch. That one punch to Biff’s face completely changed George’s whole trajectory from insecure buffoon to a confident and competent man. Every man faces a decision: Which George McFly does he want to be? The second George McFly found the courage to stand up to a tyrant and defend the girl he loved. It changed the whole course of his life. And it certainly changed the way she (and others) looked at him.
Of course, the pro-courage message was reinforced in music too. Kenny Rogers’ 1979 classic “Coward of the County” tells the story of a man who has been taught by his imprisoned father to avoid violence: “Promise me son not to do the things I’ve done; walk away from trouble if you can; it won’t mean you’re weak if you turn the other cheek…Son, you don’t have to fight to be a man.” Because of his reluctance to fight, some people think the song’s eventual hero, Tommy, must be a coward. But when the chips are down and his beloved Becky is under attack by the Gatlin boys, Tommy stands up to them and rescues her. Not a Gatlin boy was standing when Tommy was finished with them. As Tommy says in the last verse, “sometimes you gotta fight when you’re a man.”
My grandfather used to tell the Teddy Roosevelt story of the boy who got into a physical altercation to protect his sister as they were walking to church. When his Sunday School teacher found out he had fought a bully on behalf of his sister, he gave the boy a dollar as a reward. Obviously grown men should not be resorting to fist fights, but for boys it can actually be a valuable part of growing up. My grandfather used to say, "You should never start a fight, but you can certainly finish one.” Courage matters, and it especially matters to boys who want to become men. While everyone should be courageous, courage is especially a masculine virtue. We exect courage of men because men are made to protectors and defenders. The first man (Adam) had one basic task in the Garden of Eden, namely to defend its boundary. But he failed the guard the garden and, as they say, the rest if history. A man's manhood is at stake in is willingness and ability to fight, defend, and protect.
I am NOT saying that young men (or anyone else) should resort to violence to solve their problems. But neither should a young man (or anyone else) become a pacifist. In a fallen world, sometimes violence is part of the answer to the problems we face, and a man should be ready for that. How do you stop an active shooter? Not by pleading with him or negotiating with him. A good man with a gun has to kill the bad man with a gun. What’s the solution to a Hitler or a Mao? Sadly, sometimes violence is necessary to stop the bloodlust of evil dictators. And that means we must have courageous men who are ready, able, and willing to be violent, to sacrifice themselves in a fight for what is right to lay down their lives for the people and principles they love.
Men who are strong enough to be dangerous and who know how to use their strength on behalf of others are the safest men to be around. The really dangerous man is the man who can never be dangerous because he is soft, weak, cowardly. Men who lack courage not only cannot protect themselves, they are cannot protect others either. They are practically useless. Their weakness opens the door to tyrants and bullies. Of course, the most important battles we face in life and the greatest acts of courage rarely involve fighting, unless we are called to the battlefield. But there are still battles to be fought. In our day, it takes great courage to stand up for what is true, good, and beautiful. It takes great courage to stand up for God’s Word and the gospel in an increasingly hostile public square. In our day, the “coward of the county” is the Christian who is too fearful to let anyone know what he believes about homosexuality or transgenderism. The Daniel LaRusso, the George McFly, the Tommy of today is the Christian who boldly speaks God's truth despite the hostility he will face and the very real threat of being cancelled. In our day, moral courage is needed even more than physical courage -- and moral courage is harder to come by. Young men should see acts of physical courage as a launching pad for learning how to exercise moral courage when need arises.
When one acts as a coward, he damages his own confidence and sense of self-respect. A man who fails to stand up for what he knows is right, even in small ways, diminishes himself. A cowardly man is impotent. He becomes a smaller and smaller man each time he has a failure of nerve. His masculinity shrinks. By contrast, when one acts in a courageous way, speaking or doing what is right even if there is a cost, he makes himself more confident and bold. Courage breeds courage. Bravery births even greater bravery. A small act of courage paves the way for greater acts of courage. Act with courage in small ways right now and you will be preparing yourself for the next go round, when the stakes are even higher.
The book of Daniel is a good illustration. Early in the book, Daniel acts with courage in the small matter of diet. In chapter 1, he proposes an alternative so that he and his friends would not defile themselves with the king’s fare. This prepares for a much greater act of courage later in the book when his political enemies try to frame him by using his religious devotion against him. They get the king to decree that all prayers in the empire must be directed to him; in other words, they get the king to decree state-enforced idolatry. Daniel flatly disobeyed the order and continued with his usual pattern of praying towards Jerusalem, to YHWH, in front of open windows. Daniel was courageously faithful, even if meant disobeying the king and putting his life on the line. You know how the story goes: Daniel gets thrown into the lion’s den as punishment for his prayer, but the Lord shuts the moths of the lions. Daniel is then promoted and his political enemies are the ones who get eaten alive. The small act of courage in Daniel 1 shaped his life and prepared him for the much greater act of courage in chapter 6 which shaped the whole empire.
Men, especially Christian men, are made to fight — to fight spiritually, physically, intellectually, culturally, politically. Men were designed to protectors and providers, which means men were made to be fighters. Christians, male and female alike, are called upon to fight manfully in the war against the world, the flesh, and the devil. Why "manfully"? Because the archetypical warrior is masculine. Paul tells the Corinthian Christians to “Be watchful, stand firm in the faith, act like men, be strong" (cf. 1 Cor. 16:13). Sadly too many men today are like the Babylonians Jeremiah prophesied against: “[Her soldiers] have become women….The warriors of Babylon have ceased fighting; they remain in their strongholds; their strength has failed; they have become women" (50:37; 51:30). Christian men who have allowed themselves to be emasculated are a disgrace to their sex and to their faith.
G. K. Chesteron said the true Christian soldier "fights not because he hates what is in front of him, but because he loves what is behind him.” Of course, Chesterton was just echoing Nehemiah who called upon the men of Jerusalem, when they were surrounded by enemies and had their backs (quite literally) up against the wall they had just rebuilt, "Do not be afraid of them. Remember the Lord, great and awesome, and fight for your brethren, your sons, your daughters, your wives, and your houses.” The Christian man fights because he loves, and he fights for what he loves.