I don't like studying and I think nobody likes studying at school. ( at school比in school更常见，因为school不是一个大地点，所以用at。如果是一个大地点，例如一个城市，我们说in)
However, if I don't study, I won't have a good mark. (写作时，however比but更为正式。But更偏向口语）
I must study very hard, although I don't like it.
Sometimes I want to have some fun, so I don't study hard. （中文说“有时我想玩”，但是英文却不是用Play来解释的，英语里说have fun.如果说i want to have fun,就是我想要找点乐趣，也就近乎与“玩”了）
My parents are a bit worried about me, and they always urge me, "Don't watch TV and don't go online! You must study!" (这里你也可以说they always say to me, 不过我觉得Urge是“劝”，可能更有那种你想表达的意思）
I appreciate that they help me so much（thank是一个动词(有时也做名词），所以应该是i thank...he thanks，不过即使你用了i thank them,这种表达也是几乎没人说的。有一种可以是，i thank them for helping me so much.但是我觉得thank them，听起来多多少少别扭。所以你可以用一个更高级的词，appreciate,感激。还有一个问题就是，they help me more.如果前面你有提到他们帮主你什么，你可以说more，这里只要说很多就可以了。)
They love me, I know.
I always talk to myself, (跟谁说话的时候，可以说talk to someone,talk with someone，但是talk with someone是和一个人说话，当你想表达“对自己说”的时候=talk to myself) and promise myself that i must do well. (不要前面用现代时，后面用过去时。前面说talk to myself,又说say to myself太过重复。所以换成Promise）
But I can't stick to my promise for many days or even months.
Maybe this is why I don't usually get a good mark.
（it's about why...如果你换成this is why...强调性会更强）
(写好作文的一个因素就是，一个词不要一直重复着用。你可以换换别的词。你这里用了很多的always,其实代替always的，还有often,usually,frequently等等。你可以换一换。一种意思用很多方法说，才可以避免重复）
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