There is more sorrow in the life of these people than happiness. They always seem to suffer from a silent loneliness.

I quite agree with most of your points but i disagree with this highlited points above.
Reason because I'm introvert myself and can tell you i'm one of the most happy person you can ever met.

I do not like to talk too much or mingle with a lot of people because i have master the act of enjoying my own company.