小题1:are→ were

小题2:and → but

小题3:disappointing → disappointed

小题4:去掉why / why→ that

小题5:with → for

小题6:their → your 

小题7:went→ goes  

小题8:parts → part

小题9:independent → independently

小题10:在because后加if

题目分析：

小题1:You said in your letter that you are always trying to improve

主语从句中的谓语动词said为过去时，宾语从句也应用过去时，故are→ were。

小题2:your English, and your English teacher didn’t appear to appreciate

前后分句的关系为转折关系，故and → but。

小题3:your efforts. So you felt disappointing and lost the desire to learn

主语为You，应是感到失望的，故disappointing → disappointed。

小题4:English. You know why teachers are busy and maybe your teacher

know后的宾语从句叙述的是客观事实，应用that引导或省略that，故去掉why / why→ that。

小题5:is struggling to provide personal attention with all the students

provide sth for sb故with → for。

小题6:in their class. In my opinion, it is a fact of life that sometimes                                             

in their class 与本句中的your teacher矛盾，故their → your。

小题7:people’s hard work went unnoticed. Though it is nice to receive

这里叙述的是客观事实，应用一般现在时，故went→ goes。 

小题8:encouragement and support, parts of growing up is learning to be

系动词为is，parts应为单数，故parts → part。

小题9:motivated and study independent. So keep on working hard

study为动词，应用副词修饰，故independent → independently。

小题10:at your English because you stop, you are sure to fail.

Because后两个句子，应将you stop前加上if。故在because后加if。