Very often people are timid because they are afraid not reflect invented rules. Naturally, it is impeding communication. Do not be afraid of what you are convicted. If you can not make a commitment, discard them. Many people try to stick simply because they are afraid to say "no." If you understand that your consent to something infringe your rights, resolutely refused. You do not have to obey others.
Never make excuses. If you have done a certain way, then you have my reasons. Not necessary to prove to everyone that you just could not do otherwise in a particular situation. Do not think that you strongly condemn. The right to do as he sees fit, have each person. Of course, if it is not a violation of the laws.
You can do wrong, make a mistake, misjudged the situation, do not understand something, do not know what the others know. And this is perfectly normal. After all, you are an ordinary person, and does not need to be perfect in everything. All make certain mistakes, remember about it. If you realize that you did wrong, think about how not to repeat such mistakes in the future, not about the fact that now people think about you. Admit your mistakes, and after a while you become a more confident person.
Always evolving. If you regularly receive new knowledge, you will feel more confident. You can start with the basics - daily read literature. Moreover, preference should be given not Pulp Fiction, and the classics. You can also start learning foreign languages or to enroll. Smarter than you become, the less reason you will have to shyness.