Well, let us remember that strictly speaking a theme is a comment or lesson about life that can be learnt from the story. You have just chosen a quote that is more accurately a topic. The question you need to ask yourself is what is the author saying through this topic. I will help by giving you a few quotes to think about that should hopefully get you started and help you to consider this in more detail.
The most appropriate quote that you need to consider comes in the final paragraph of the story, and comes just after the quote that you have chosen to base your essay on. Describing the experience of falling with her mother after being rescued from the burning house, the narrator says:
Curled as I was, against her stomach, I was not startled by the cries of the crowd or the looking faces. The wind roared and beat its hot breath at our back, and flames whistled. I slowly wondered what would happen if we missed the circle or bounced out of it. Then I wrapped my hands around my mother's hands.
You might like to consider the way that the narrator experiences a tremendous sense of calm and unity whilst going through quite a scary experience. This of course is paralleled in the first accident that the narrator's mother experienced, when she told her daughter:
My mother once said that I'd be amazed at how many things a person can do within the act of falling... But I also think she meant that even in that awful doomed second one could think, for she certainly did.
Perhaps the story's message in relation to the topic you have selected relates to the elasticity of time, and the way that even in a fall that takes a second it sometimes feels that we have hours to think and respond.
Well, I usually make my own quotes and then try and lead my essay from there. The world is full of quotes and your teacher would not have the time to check whether it actually exists. As long it is not
Nonsensicle, it wont really matter.
For example:- As long as you have not reached the end of your means, the ball is still in your court.