Would you please help me with this?

Could you help me with this? Does this flow well and is this free from any mistakes?

My proudest moment in my life is when I participated in a speech contest. When I was in high school, I was so shy and withdrawn that I was aways afraid of expressing myself. However, I decided to enter the speech contest because I took it as a great opportunity to change myself. Although I came in last, I tried my best to overcome my shyness, and through that experience, I gained more confidence in speaking in public.