In our normal state, there is nothing happy or angry. What do our faces give people? Is it serious that the smile is unnatural?

Very normal, dull expression, can show a natural state, little emotional change. It depends on who you are communicating with, or what state you want to show on what occasion, which will give people a feeling.

The expression may naturally make people feel cold and serious, which may be the prejudice of a few people, because the expression of your expression is the opposite of what they present, and this contrast will make the other party have a thinking prejudice against you, but in fact, the other party is not malicious, just different in cognition.

Pure personal opinion, for reference only, thank you.