Yesterday I just realised that I was a handsome person.

Jackson6612 wrote:

Here rules of English of grammar are contradicting the real life situations. Don't you think?

No, I don't think so. You can use a present tense if the statement is still true in the present.

Yesterday I learnt that London is the capital of the UK.

Mary told me that she is living with her boyfriend.

When I was in school, I learnt that water boils when heated to 100°C.

Jackson6612 wrote:

Which of the following sentences is correct? 1: Yesterday I just realised that I was a handsome person. 2: Yesterday I just realised that I am a handsome person. Probably you would say that only sentence #1 is correct according to the rule of concordance of tenses in a certain sentence. But I don't think sentence #2 should be considered incorrect. If yesterday I was a handsome person, then in one night things do not change to such an extent that the very next day I would become an ugly person. Here rules of English of grammar are contradicting the real life situations. Don't you think?

Hi Clive,

Yes, there was a mistake in sentence #2. Now I have corrected it.

Best wishes, Jackson

I think that with "realizing" (even more than most other actions) using the present tense makes perfect sense, unless the situation has changed since you reached your realization.

(Don't use "just" though, at least not in that position.)

Just yesterday, I finally realized that although I am fat, I am happy, and I'm not going to diet anymore!

Yesterday, I was looking at pictures of myself in high school, and I realized I was really fat! Joining the track team in college sure made a difference. 

However, you certainly can use was even if the situation is still true. (Many months ago, I made a post that implied this wasn't true. I'm wiser now, so please don't find that post and ask me to explain the contradiction.)