假定英语课上老师要求同桌之间交换修改作文，请你修改你同桌写的以下作文。文中共有10处语言错误，每句中最多有两处。每处错误仅涉及一个单词的增加、删除或修改。
增加：在却此处加一个漏字符号（∧），并在其下面写出该加的词。
删除：把多余的词用斜线（\）划掉。
修改：在错的词下面画一横线，并在该词下面写出修改后的词。
注意：1.每处错误及其修改均仅限一词；
2.只允许修改10处，多者（从第11处起）不计分。
Dear David,
I have recently felt guilty, stay sleepless at night. You may wonder how. To tell you the truth, it is just because of the fact that I seldom cheat in exams and I just can’t stop me. In many exams, I used cellphones to surf the net for answer. Besides, I sometimes referred them to my notebooks so copied something. As you know, cheating do much harm to our learning and self-confidence. It’s time that I take action to stop it. I would appreciate it you could offer me some advice.
Looking forward to your reply!