When I was about 13 my Japanese tutor said I was 真面目な人.
He said, do you know what that means?
I said, oh yes, you think I am in earnest.
He said, what I mean is that you are not hasty and you do not change your mind about people.
He explained that Westerners might feel one way about someone they meet and then that view might go through numerous transformations over the course of months or years; for a Japanese person, he said, how you relate to somebody is something that takes shape in its own time, and then the outward form of the relationship might change but the inner substance ideally does not.
I don't know how he could have formed that impression when I was a spiky unpleasant 13 year old but I think it has been true for me. My feelings about people are resistant to change. I feel the same way about people I met 10, 15, 20, 25 years ago as I did when those feelings first formed.
The cultural difference as he perceived it is something I sometimes think about.