You'e probably hearf the expression "fake it until you make it!"  Yes, it can sort off work in the short term - in my expereince, not in the long term.

People waste a lot of time thinking about their body language when they should be working on how they really feel on the inside and then their body language will reflect that.

It’s tempting to pretend to yourself and to others that you’re OK. You don’t want to admit that anything is wrong because you see that as a weakness or a failing, as if going through a hard time somehow makes you less of a person.

Showing vulnerability doesn’t reveal weakness. Actually, it’s the opposite. It’s a sign of strength. You need to have a certain level of confidence to show vulnerability.

'Worth a Read'
Feeel the Fear and Beyond, Susan Jeffers
https://susanjeffers.com/books/feel-the-fear-and-beyond/