'the four hundred meters athlete' - extracurricular activities or work experience

i really need help in improving my paragraph here,,, its on the common app.. thanks

I am the four hundred meters athlete in my freshman and sophomore years. To me, stamina, strength, willpower and concentration are the four essential components in racing the four hundred meters. The race is not long or short, but I have to use my whole concentration into the race. However, it's not only a race, but a higher level training of abiding willpower and strength. Although the training of an athlete is sometimes toilsome and we wanted to give up, we have to endure and overcome. By overcoming the adversities in training, it helps me in persisting to do everything and not giving it up. The race also requires athletes to follow the direction and not getting out of line. Unfortunately, after I got injured from the swimming gala, i stopped my training and started to develop another hobby, which is playing the piano. I benefit a lot from this sport since it gave me a really clear objective in my life.

Feel free to state the mistakes... thanks a lot

I was the four hundred meter athlete during my freshman and sophomore years. To me, stamina, strength, willpower and concentration are the four essential components in racing the four hundred meters. The race is neither too long or too short, but I have to put my whole concentration into the race. It is not only a race, but a higher level of training for my abiding willpower and strength. Although, training for an athlete is sometimes toilsome and I want to give up, I have to endure and overcome this. By overcoming the adversities in training, it has helped me to persist in everything I do and not give up. Unfortunately, after I became injured from the swimming gala, which indicated that, I can't do it anymore. I benefit a lot from this sport since it gave me a really clear objective in my life.

All of a sudden you just stop the paragraph, you need to ease the reader into ending it. Also, I didn't make my corrections red I'm sorry hope I helped! :)