There is nothing wrong with being shy, nor should you let people push you around say things like "grow up". But, if you feel that being shy is a problem and it is something you truly want to overcome, if it is important to
you then there are many ways to get this result.
1. Find something you love, something you are passionate about and get involved with a group of people that share your interest. Like a meetup.com group. There you will have the safety of talking with like-minded people and that is a good place to start.
2. As someone else pointed out, learn to be comfortable with the uncomfortable. So what if they are judging you, let them. Ask them if they really are. I bet you will find that more often than not, you are mind reading them and unless you are confident of your telepathic powers- what you think they are doing is probably wrong or blow out of proportion.
3. Take a communication class such as NLP, toastmasters, or anything else that you can find in your local area. There you will find a supporting environment where you can have people help you get over your shyness.
4. Give it time, it takes a lot of time to learn new behavior and if shyness is part of your core personality it may take years to become more confident.
And finally, try not to be so serious about it, it only makes it harder to learn. Be playful and curious, explore where you boundary is and push past it. Whats the worst that could happen?
I have many articles about meditation and yoga and some of these may help also. You are welcome to check out my website:
Meditation Secrets Revealed
Playfully yours,
Vlad