This morning I finally said to Mom, "Please come to the game this Saturday. It's the first play-off game, and I'll be the catcher." But Mom said, "Well... I'd like to, but I'll be busy that day. Maybe next time, Sangho." I'm disappointed because this is a very important game for me.

Received my report card this afternoon. I got many bad grades. Minho also received his report card, and he was at the top of his class. Mom said to me, "You can do better next time." But maybe I'm not as smart as Minho. Well, cheer up, Sangho!
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This is a diary. Would you check the sentences, please? Can we use "Received my report card..." without the subject "I"?

This looks great.

In formal writing, you need a subject, but since this is a diary, this can be informal and omit the subject.

Yes, we can use "Received my report card this afternoon" without explicitly including the subject "I." In this case, it is implied that the person speaking is the subject and is referring to their own report card. Using pronouns and omitting the subject is common in diary entries or casual writing styles.