Diary - Today, my English teacher discussed personality with me.

[emsr2d2]

Can I use the past tense for the whole sentence? Is that acceptable? Sometimes, when I read novels, I found find they use the past tense for the whole book.

Again, you're expressing a general fact about the novels you read so the present tense is appropriate there.

She knew that most companies looked for outgoing people but she was not like that.

That's grammatically correct. It does, however, leave open the possibility that she is now "like that".

 

[Tarheel]

@Maybo I would say it simpler, thus:

Some of the novels I have read use past tense for the whole book.