Those players put in all they have for a single moment in their career, some breaking their bodies to the point of not having a great life in the future just to be a hero for one moment.
So what is your main character's goal in life. Doesn't have to be the point of your current book, but in their life beyond the pages. Now good books tie this goal into the plot of their book, but think about it. Harry Potter's life isn't all about defeating Voldemort, he wants to live his life to the fullest and Voldemort just happens to be in the way.
So if you take the obstacle out of Harry's way he would still get to live his life to the fullest, now don't get me wrong, without Voldemort, their would be no books. And that's the point of a book, the conflict and resolution. I am talking about something more though. What is your character's life goal? Its the key to their being and showing what they want is important to their development.
So what is your character's goal in life? To be a teacher? To solve the space time continuum? To be a stay at home mother? To be a police officer? What is it they want more than anything else and would still strive for even if they weren't in your book?