As viewers watching from outside the court, or from a TV screen, we rarely get to a glimpse of an athlete's vulnerable side. One can only imagine how Serena Williams must have felt after losing to opponent Roberta Vinci in the 2015 U.S. Open. 

Now, a new documentary directed by Ryan White aims to give viewers a rare and personal look into how Williams dealt with the disappointment. In one markedly human moment in Serena: The Other Side of Greatness, the athlete laments her stunning loss after the U.S. Open. "I've never been so close to having something and then losing it. I've been in a really dark hole. I feel like I've let a lot of people down," she says, clutching a stuffed animal and refusing to look directly at the camera.

Following the event, Williams refused to speak to reporters for several days. (Instead, she focused on the debut of her fall collection at New York Fashion Week.) At the time, one journalist remarked that she is "one of the most self-aware athletes on the planet, one who has more nuance than a Truffaut film." Of course, White's documentary, which premiered on EPIX last Wednesday, may not be at the level of the lauded French New Wave filmmaker François Truffaut  -- but it is deeply nuanced, and mostly follows Williams' historic 2015 professional run, in which she nearly won every major title all in the same year.

"Serena is always surrounded by people -- she is never alone," White told "That can be a nightmare for a documentary filmmaker, because all you want is those quiet moments," he said, adding that he especially treasured scenes where he and Serena had direct conversations.

For business leaders, the film presents many valuable lessons on overcoming adversity and accepting heartbreak:

1. Emotions are important to your success.

A seminal moment during the film is when the Williams sisters are shown competing at the Indian Wells Tournament in Indian Wells, Calif., back in 2001. Amid allegations that their father had fixed matches, the predominately white crowd booed the Williams as they descended onto the court. Williams admits that she cried all the way home. 

"Tennis has always been a very lily white sport," Williams' agent remarks in the film. "People may think she's controversial, but I think her race has a lot do with it," she adds. 

Williams, on the other hand, doesn't view herself as a very controversial player. "Maybe because I'm black, I must be controversial and they think I like drama," she said. "I get angry on the court, but so do a lot of players. I'm an intense player. I play with my heart out."

For entrepreneurs, passion and perseverance are key ingredients to success. Channeling your feelings and energy into you career can be a good thing.

2. The strongest leaders know how to forgive.

For fifteen years, Williams boycotted the Indian Wells tournament. Then, in 2016, she decided to face the past.

"I went to Africa and I met Nelson Mandela," Williams recalls during the film. "He was in jail for the prime of his life. Not only did he forgive the people that jailed him, he became friends with them, and didn't hold a grudge against them." The experience taught her a valuable lesson: "It's better to truly, honestly, wholly forgive, by going back."

In order to forgive, you shouldn't--and probably cannot--forget. Forgiving means rising above what others think, for the sake of moving on with your life. 

3. Pressure is a positive thing. 

The very first scene of the film depicts Williams getting ready for a match. In a voiceover, she explains why pressure is almost always a positive thing: It indicates that you're on to something great. 

"Would you rather not be the best, or would you rather be on the verge of doing something special?" she says, emerging from the locker room into the sunlight, amid a crowd of roaring fans.

Stress may not feel great, but it's worth considering that the emotion is a sign that you're moving in the right direction, and challenging yourself along the way.