I'm a student of college who major in English. Last year, I took part in an English speech contest hold in our city. I prepared very hardly for it and practiced over and over again. Unluckily, I got the second place in the contest. But I was not satisfied with the result. I thought I could have done better if I had been more confident. Now I realize that self-confidence is very important in many field. If we lack of confidence, we may be afraid of doing things we can do well. Therefore, we should build up our self-confidence and face the challenges bravely.

答案解析：

1.第一句中的“college”前面应加上冠词“a”，表示“一个大学生”。所以应改为“a college”。

2.“who major in English”中“major”为动词，而句子中缺少谓语，应使用“major”的第三人称单数形式
“majors”。所以应改为“who majors in English”。

3.“hold in our city”前缺少被动语态的助动词“was”，因为“contest”与“hold”之间是被动关系。所以应改为“held in our city”。

4.“I prepared very hardly for it”中“hardly”表示“几乎不”，与句意不符，应使用“hard”表示“努力地”。所以应改为“I prepared very hard for it”。

5.“Unluckily, I got the second place in the contest.”中“the second place”通常不表示“第二名”，而是“第二名之后的位置”，应改为“second place”或“the first place”。由于后文提到作者不满意这个结果，所以这里应改为“second place”。

6.“many field”中“field”为可数名词，前面有“many”修饰，应使用复数形式。所以应改为“many fields”。

7.“If we lack of confidence”中“lack”为动词，表示“缺乏”，后面不需要介词“of”。所以应改为“If we lack confidence”。