He said that he never went on the platform without fear and trembling, and would often be covered with cold perspiration.
There are many worthy people who are brave on the street, who would walk up to a cannon's mouth in battle, but who are cowards in the drawing-room, and dare not express an opinion in the social circle.
They feel conscious of a subtle tyranny in society's code, which locks their lips and ties their tongues.

Addison was one of the purest writers of English and a perfect master of the pen, but he could scarcely utter a dozen words in conversation without being embarrassed.
Shakespeare was very shy.

He retired from London at forty, and did not try to publish or preserve one of his plays.

He took second or third-rate parts on account of his diffidence.
Generally shyness comes from a person thinking too much about himself--which in itself is a breach of good breeding--and wondering what other people think about him.
"I was once very shy," said Sydney Smith, "but it was not long before I made two very useful discoveries; first, that all mankind were not solely employed in observing me; and next, that shamming was of no use; that the world was very clear-sighted, and soon estimated a man at his true value.

This cured me." What a misfortune it is to go through life apparently encased in ice, yet all the while full of kindly, cordial feeling for one's fellow men! Shy people are always distrustful of their powers and look upon their lack of confidence as a weakness or lack of ability, when it may indicate quite the reverse.