With each new sport came a desire to become the best I could be
Why? How does this relate to the importance of self-improvement? This sounds like you were only trying to please your mother.
I had been obsessive over being good at sports, which left me with no care for academics.
This indicates an obsessive personality on your part. That could be seen as a negative by the reviewer. Why not skip this line and instead, focus on explaining how sports taught you how to value academics as well and give an indicator of you consider your interest in the two as balanced.
Self improvement is not just about accomplishment. It is also about becoming a better person. The essay focuses too much on the importance of accomplishments, with little reference to the lessons you learned with regards to self-improvement. For example, why did you feel a need to improve your community relationship? How is this relevant to self improvement?