I love this quote. Its origin isn't known, but I first came across it in an iconic Harley Davidson ad.
To me, the quote is meaningful in several different ways. Fundamentally, it means that you have to be in control of your own life. You chart your own course and don't stop until you reach your final destination.
It means that you're the captain of your ship and sometimes you have to steer that ship through stormy seas until you complete your journey and are in a safe harbor. You don't let anyone or anything lead you off course. You stay firmly at the helm until your journey is a success. You're responsible for your crew and the passengers and you may have to ride tumultuous waves to get them home. In business your crew and your passengers are your employees and your customers. As captain you have a duty to them. Honor over profit. Honesty over short-term gain. Passion for others over Greed.
Let's look at the quote again: "When writing the story of your life, don't let anyone else hold the pen."
The other key meaning I take from this is literally don't let anyone else write your story. You know as a unique individual who you are and what you contribute to the world. You know that you're an inherently decent person. You know what's in your heart. Always make sure that the truth comes out and don't allow other individuals with different motives and agendas of their own to misrepresent who you are or what you have done.
It's a sad fact of life that there will be occasions when people put their own spin on events and it doesn't represent reality. That's why you have to always speak up for yourself. If you don't, you can't expect anyone else to. Don't let inaccuracies or untruths become common perception. Speak up and stand up for yourself. Don't let them take the pen away from you.
You have to wield the pen and write the chapters of your life both in terms of the actions that you take and how they are recorded in your own history.
The same Harley Davidson ad that carried the above quote also included a great subhead: "You say you want to ride. Now say you will. It's time to start something."
So, start your chapter and make sure your writing each word with passion.