Unfortunately the only solution is talking to people. Practice makes perfect, face your fears, and so on.

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If you talk to people enough, you'll get used to it.

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But don't force it too much, go at your own place. Always just a little step out of your comfort zone.

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I struggle with the same thing, and successfully talking to someone can give a euphoric feeling of accomplishment - it's worth trying just for that.

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(I called a stewardess and asked for water when I was thirsty on an airplane today - an example of what I mean by little accomplishments)