I'm not sure if this is exactly the same thing, but I used to be very socially timid. Then, in high school, I went to Japan for 7 weeks as a foreign exchange student. When I came back, I was no longer "da mouse" (my old nickname).
It may be drastic, but it would certainly be fun to find some program that lasts a few weeks that dumps you into a completely different culture. It's inevitable that you're going to make a complete idiot of yourself at least a few times (in probability, many more than that), and after that experience, you come to realize that it's really not that big of a deal. You'll also meet so many wonderful, kind people that you'll realize that people are NOT out to get you, and are NOT out to find all of your flaws. (That's reserved for family members, lol.)
Also, it's very egocentric to think that people actually care that much about you and what you do. May sound harsh, but it's true. I really liked Erin's example of jumping, fully clothed, into a busy pool. Did anybody care? No. I use henna to dye my hair, which involves leaving weird-smelling green goo all over your head for up to four hours. The first time I had to go out with henna head, I was kind of nervous. But I actually went to a restaurant with my BF with smelly green goo and saran wrap on my head an nobody batted an eye. It was almost disappointing.
As far as caring what others think about your decisions -- there are certain instances where you should care (if you're going for a promotion, for example) but in the vast majority of cases, the standards you think someone else has for you are MILES higher than they are in reality. People generally don't start out with high expectations for somebody (it saves them disappointment); it's after working together for a while that the expectations start to raise -- all based on past performance. If you're mindful, it's really difficult to screw up so bad that you *legitimately* disappoint someone. Again, close relatives are the exception.
They can be a little bit unreasonable. Especially if they're your inlaws.
This is your life. As far as you can be sure of, everybody else is a figment of your imagination. Why go out of your way caring what imaginary people think of you? Because even if they aren't imaginary -- what you think they're thinking is completely illusitory.