Many insecurities, fears, and doubts stem from lack of understanding or lack of knowledge about something. The more you understand and know about a situation, the more comfortable you will be and thus the less power your shyness will have over you.
Let’s take for example the subject of public speaking. This is an activity that terrifies most people half to death, but only because most people don’t have much knowledge about it. If you do some research and investigation, you’ll come to learn that it’s perfectly natural to be terrified of public speaking, and that almost every single person has the same fears and insecurities that you do.
When you take it further and ask yourself why you are so terrified of this, you’ll come to learn that you are scared of being judged, or of being laughed at. From there, you can go and read and learn about people who are good at public speaking—learn their tips and strategies.
This way you are much more prepared because your knowledge on the subject is vast. As a result of this, your confidence will already be much higher than before, which might allow you to attempt public speaking when you join a club like Toastmasters. As you practice more, you will naturally become even more confident.
This rule applies to any area where you feel insecure. Read and research as much about the topic as possible. This will help increase your confidence enough to give the activity a try to see if you might be able to become better at it. And that initial confidence to take action is all you need to get the ball rolling and overcome your shyness.