Difficulty Expression Feelings and Emotions

For me, showing any sort of personality to anyone i'm not practically family with is impossible.

it used to be really hard for me to express emotion and feeling, but now i kinda learned how to do that, don't know how..

I can only show all my emotions to people I trust 100%, and that isn't a lot of people.

It's kinda weird, though;
- 'Cause when I meet people for the very first time, for example if I'm at the grocery store and someone starts to small talk with me, I am able to smile and show happiness and sometimes even (vague) disappointment - if they seem like nice people, which most do.
- But when I get to know them better, I shut down. I rarely smile, I don't show happiness, and especially not sadness or disappointment! I probably seem like I'm an ice cold rock or something.
- But then, if I get to know them even better and I trust them 100%, that's when I can show my emotions and this wall finally breaks down.

I guess there are only a few people in the entire world that doesn't think I'm an ice cold stone.