If you think that you can't do this work then ask yourself that why can't I do this work?Ask if you have done this before or if you were not successful in achieving that.It may be possible that this time you will succeed.
Deep breathing exercises
If your throat is dry and palpitation starts ,these are actually sign of nervousness.To control that take deep breath.With the help of yoga , meditation and practising deep breathing,you can control stresses within you.This will give peace of mind.
Question-Answer round for you.
Think yourself as an interviewer and ask yourself question and then answer them.This will build up your self confidence if you do this exercise thrice in a day and that too in front of mirror.
Set realistic targets
Sometime little pressure or stress works for you.Take decision that will initiate communication with people.Listen to the people and give them your ears.Always reply even if you take little more time.don't bother what other will think of you and consider yourself the most intelligent and talented person.
Slowly but steadily
Participate in day today communication like blogs, start speaking in public and participate in presentations.
Above all give yourself time because you worth it.Its not about selfishness instead its about happiness.If you are happy with you ,you can make happy people [family,friends and others]around you.But if you are not happy within ,you will gradually loose interest in people around you too.Be true to yourself first .Be real one and not fake.