I'm not myself today.

我今天心神不宁，不在状态

Sorry, I'm not myself today. My son just had a severe fever.

对不起，我今天心神不宁，我儿子得了严重的发烧。

A:We had a meeting at 10 o'clock. Where were you?

我们今天十点有一个会议，你在哪里?

B:I'm sorry, I guess I forgot.

对不起，我想我忘了。

A:Forgot? How could you forget?

忘了?你怎么会忘了?

B:I don't know. I'm not myself today.

我不知道，我今天心神不宁。

A:What's wrong?

你怎么了?

B：Maybe I'm just tired. I haven't been getting much sleep.

或许我只是累了。我一直睡不够。