If you are quiet, that’s fine.
If you are shy, that’s fine.
If you don’t recognize the difference, that’s not fine.
To clear the air, shy is defined as being easily frightened away whereas quiet is defined as being refrained in speech or saying little.
I am not afraid to speak to other people, but I will not start a conversation with someone I have never met. I am quiet.
He is afraid to talk out loud and replies nervously when spoken to. He is shy.
It’s awesome if you share your life story with everyone you don’t know, but just because someone doesn’t do the same doesn’t mean they have no life.
It is possible someone doesn’t tell everyone how their day was simply because they don’t expect you to care nor do they care how your day was. That would be a perfect example of someone who is quiet.
Maybe, someone has been shut down so frequently throughout their life they are genuinely afraid to talk. That person is shy.
See the difference?
Neither one is wrong — neither one changes your morals, hobbies, or interests. It’s just the way a person is.
Whether they’re quiet or shy, why do we shame them? Rather than picking on someone as “the quiet/shy kid who has no friends,” we should build them up. Just because someone is shy doesn’t mean they aren’t cool.
Just because someone is quiet doesn’t mean they have no friends. And vise versa. They might love to party, or they might not. Maybe they’ve been to every country in the world. Maybe they can speak five different languages.
You don’t know.
That’s the most beautiful thing about those who speak rarely. They are mysterious. Undiscovered.
My best friend is quiet. She also has a high self-esteem but isn’t cocky. She isn’t necessarily outgoing, but she has many friends. When you talk to her for the first time, her sarcastic sense of humor surprises you.
But, she’s quiet. There’s nothing wrong with her. However, there is something wrong with you if you wouldn’t give her, or anyone similar, a chance.
If you’re naturally outgoing, don’t change yourself. But give that quiet person a try. Ask them something. Ask them anything and everything.

Shy
1. Bashful; retiring.
2. Easily frightened away; timid.
3. Suspicious; distrustful: I am a bit shy of that sort of person.
4. Reluctant; wary.

Quiet
1. Making no noise or sound, especially no disturbing sound
2. Free, or comparatively free, from noise
3. Silent
4. Restrained in speech, manner, etc.; saying little
5. Free from disturbance or tumult; tranquil; peaceful

Definitions from dictionary.com.