It takes more than a pair of testicles to achieve manhood. Myriad cultures around the world have rites of passage to symbolize it. This article focuses on the journey from boyhood to manhood, rather than any fundamental difference between men and women.
1. Know yourself. Understand that all men in all cultures may have, to some extent, been socialized in ways that may be psychologically and culturally damaging, and may bring unhappiness. The first step in creating a sense of self in manhood is to examine the environment in which you were raised, as objectively as you can.
Did you grow up in a culture where it was acceptable to abuse someone, whether physically or verbally, who was 'out of line' or insubordinate? Violence is more often the result of cowardice than a genuine impulse to solve a problem; it's a reaction to frustration, a desperate seizure of power when nothing else is going your way. Using violence or threats against friends or family to "show your authority" is unhealthy and damaging. Dozens of philosophies and world cultures affirm that violence is only acceptable as a means of protection from imminent danger.
Were you taught to be "tough" to the extent that you were taught to suppress emotion, to hold in tears and never expose vulnerability? The drawback here is that you also learn to internalize and suppress these emotions which then fester and escape in undesirable ways. Focus on being tough to the extent that you can be a reliable, strong figure who can handle adversity. Sometimes you must do unpleasant things for the sake of the people you care for, and this requires toughness, but find healthy ways to vent as well.
Were you taught to hate/fear anyone who's homosexual? Understand that only one thing makes you gay: having a romantic and sexual preference for people of the same gender. The kind of music you like, the clothes you wear, whether you cry at sad movies, buying your wife flowers, being sensitive or nice to others, none of that makes you gay. Furthermore, outward displays of homophobia indicate a man's own sexual insecurity.
2. Develop yourself. Your body changed from that of a boy to that of a man, and so should your mind and heart. A boy trapped in a man's body is not a man at all. Think about any stereotypes you were taught (from the previous steps) and how you can overcome them. Understand that this process will differ dramatically from man to man, and will continue throughout your life. The important thing is that you learn and mature as time goes on.
3. Seek responsibility and take responsibility for your actions. The main difference between a man and a boy, and adult and a child, is that men are responsible. Men honor their commitments, accept their duties and are accountable for damages they incur, debts they owe and claims they make. Men clean up after themselves (figuratively and literally). Men know that anyone can father a baby but only a man who understands and accepts responsibility can be a good father. Men refuse to make anyone do anything they themselves are unwilling to do. Sometimes men make sacrifices for the people they love and care about. That's life. It's part of growing up, whether you like it or not. The difference between a man and a boy is that a man steps up to the plate, while a boy hesitates or complains. A man admits when he is wrong
4. Be a good man. It can be tempting to think that by meeting your self-defined responsibilities as a man, your job is done, but that doesn't necessarily make you a good person. Never stop trying to do the right thing and re-evaluating your character and integrity. If you're going to be a man, be a good man, or else it's no better than remaining a boy.