Stop obsessing over every little thing that you might feel like saying — essentially pre-editing yourself out of many good conversations before they can even begin!
I used to do this all the time: pre-judging and PRE-REJECTING everything that I was about to say before the words ever made it out of me. You feel like others are constantly judging your thoughts and ideas every second of the day, and this kind of intense scrutiny — imaginary or not — is difficult to hold up under. It’s little wonder that you are reluctant to speak up! I think this is why introverts find people to be more a source of stress to them rather than of comfort. It’s also one of the major reasons why being social may feel like such a chore for you, when it can often seem like such a breeze to most everyone else.

The sad part is that the entire underlying dynamic causing this pre-rejecting response (i.e., the intense scrutiny of others) doesn’t even exist in actuality. It’s entirely in your mind for the most part, and you are merely projecting all this garbage onto others and seeing what really isn’t there. This is a form of paranoia, but it’s also a form of arrogance as well. Arrogance? That’s right: after all, what makes YOU so special that everyone is always watching YOU and everything that you are doing all the time? Why do YOU deserve such constant observation? Well you don’t, and you aren’t getting any! This is all what’s known as ‘magical thinking’, and it’s an error in cognition that you need to address and overcome.

  http://highstatusmale.com/HSMblog/2010/07/20/what-every-shy-person-should-understand-about-shyness/