Why does forcefully adopting a quiet personality results in social anxiety?

I used to be very loud and outgoing, but when I got bullied quite severely I decided to act more quiet so I could get noticed less by others which resorted into me feeling unusually tense and fearful of others. It’s really strange because at one point when I forced myself to be more silent I wasn’t feeling awkward or shy. Now all of a sudden it’s hard to speak and I feel so tense and awkward. What happened and how do I reverse this?
Why does forcefully adopting a quiet personality results in social anxiety?
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