Editor's note: Alex Morgan is an Olympic Gold medalist, starting forward for the U.S. Women's National Soccer Team and author of "The Kicks," a children's book series. This open letter to the girls of the world is part of the "Girl Rising" project. CNN Films' "Girl Rising" documents extraordinary girls and the power of education to change the world.
(CNN) -- Dear Girls of the World,
I didn't start playing soccer imagining I would be scoring goals in the Olympics or representing my country at the World Cup. I started playing soccer, and sports in general, as a way to simply make friends. On the field, I was able to hang out with kids my age, kick the ball around and just have a good time.
What I didn't realize at the time was that soccer would do more for me than I could ever imagine. At a young age, soccer taught me about leadership and sportsmanship and what it means to be a good teammate. Most importantly, it taught me the power of confidence.
Confidence is not something that is always easy to find. Often, being the new girl on a team or being in a group breeds insecurities. I have joined countless teams where I was the new girl, and I was never immune to those feelings of self-doubt.
I have learned that by pushing aside those insecurities and rediscovering my inner confidence, I become a better teammate and person.
That's why I wrote the book series, "The Kicks," to show girls the importance of maintaining confidence when faced with new (and sometimes scary!) opportunities. While the book is aimed at middle schoolers, the lessons in it are ones that I think hold true across all ages.
Joining the U.S. Women's National Soccer Team was intimidating to say the least. I joined a team with women who I had looked up to for years, and at just 20, how was I supposed to fit in with them? I was nervous and overwhelmed. But I knew that I was capable of competing with them so I pushed myself outside of my comfort zone in order to be the best player I could be. I now call these girls more than just my friends. They are my sisters, and together we support each other through thick and thin. I'm so grateful to have some amazing women around me to help me learn and grow.
Confidence has carried me on and off the pitch, through high school in California, college at UC Berkeley and now professionally for the U.S. Women's National Team and the Portland Thorns. I have had to adjust to new surroundings, meet new people and have been challenged by different situations. All of those experiences, while nerve-wracking at the time, have empowered me to grow stronger.
It's important that as women, we stand up for ourselves, stand up for our peers and show the power that confidence can have for women everywhere.
-- Alex Morgan