Undergraduate / "The day of the marathon" - Help with Prompt 2 of the UC application [4]

hello! i this is my essay for prompt 2 and i really need some feedback, can please help me.
Tell us about a personal quality, talent, accomplishment, contribution or experience that is important to you. What about this quality or accomplishment makes you proud and how does it relate to the person you are?

As I heard the starting-gun fire signaling everyone to start, I felt the adrenaline rush through my body. For a brief moment I wondered if I was dreaming or if I was in fact endeavoring to complete the marathon. I never imagined that I would be among the thousands of people who completed the 26.2 miles in the Los Angeles marathon. Just seven months before, during my junior year, I joined a program called Students Run L.A. (SRLA), which helps students train for this arduous marathon. My parents were worried and questioned my physical ability, they didn't believe that I would be able to finish the race and often joked about my decision. Their jesting motivated me and I was determined to take this challenge and prove to them that even though I was not physically or mentally ready yet, I was committed to accomplishing my goal.

When I first began to train, I was completely out of shape and lacked confidence. To make things worse, I always came in last during all of my practices. My constant negativity and lack of confidence were detrimental to my mental well-being and coupled with my parents' constant negativity, I was ready to give up. Fortunately, my team members kept encouraging me to run and look at the end goal of finishing the marathon.

The week of the marathon I followed all of the instructions that were given to properly prepare my body. I drank plenty of water and followed a carbohydrate-focused diet. I also prepared mentally and envisioned myself wearing the blue sweater with the marathon emblem on it and having the shiny medal around my neck.

The day of the marathon I woke up very early feeling both anxious and excited. The first few miles I was so eager to finish the marathon, I was optimistic and constantly laughed and joked with one of my team members. The energy propelled my legs to run and it even seemed easy then. Unfortunately, the phrase, "mind over matter" escaped my thoughts and as I reached the 20th mile I was ready to give up. I knew that the pain was more physical than mental, but I couldn't ignore how my legs became weak, my feet began to throb with every step, and blisters began to form; I feared I would not be able to mentally will myself through the last 6 miles. I felt like stopping and boarding one the shuttles that picked-up runners who could not finish. My friend kept insisting to keep going, but my body kept telling me to stop. As I kept walking, an SRLA leader and his wife approached me to give me water and they noticed that I needed motivation. They stayed with me all the way to the end. After eight hours of running and walking I later reached the finish line. I broke down in tears when I saw my father's overjoyed face standing behind the finish line and the people handing out medals.

Students Run L.A. helped me achieve one of my personal goals, this program challenged me mentally, helped me create goals, and developed a sense of confidence I never knew I had. I learned that when facing a challenge it is easy to quit, but if I want to achieve a goal, I should be persistent and committed. Completing the marathon is more then running 26.2 miles, it is a metaphor for my life and how I will continue to overcome obstacles. There may be times in life when people or other obstacles can possible deter me from accomplishing my dreams, but it is my own determination and the positive influences that will help me persevere and hurdle over life's obstacles.