its simply a mindset and ability to adapt to environments. for instance in a regular setting like where you go to school or a job there is always opportunity! if you feel depressed then there are going to be many people around you who are also shy or depressed so there are people that you could connect or relate with on an emotional level, even talkative people like to be around quiet people the key seems to be choosing to not make any attempt or risk to make conversation with other people and what happens is that everyday some people wake up and never make conversation with strangers and the pattern becomes so regular that it becomes normal and that blocks any chance of meeting people.
also even though you may be shy you also have potential to be more outgoing because evolution is about change.
i believe that no matter what you look like if you raise your standards a little and you have some form of a plan of action then your life can turn around quickly, its like my friend who is cross-eyed, nobody cares that he is cross-eyed because he has a great attitude and tries hard socially.
i think one of the biggest psycholigical challenges is that there are very few cheerful people around or true/down to earth characters in the one setting, most people are either normal/shy/ordinary/followers. if we had more positive/cheerful/fearless people around us each day then that is definitely going to rub off on you or anyone else and you would have no problems expressing yourself with those people because they behave that way too.
its like the first year of my course, everyone was shy, in fact the teacher would often ask for the answer and nobody would even attempt to answer, and because everyone was quiet it became more difficult to be the person to try and lead the way in terms or being expressive because its hard to speak in a relaxed way in front of 25 people, but if you are in a class where everyone is joking around and expressive then its much easier to be that way too.
so i think alot of it is also caring too much about what others think or behave. just be yourself and say what you want without fear because the difference will be you either said something and it came out wrong or you said nothing at all which is just nothingness but after a while with enough practice and saying the wrong things you'll at least build up enough courage to say what you feel and you'll one day wake up and you'll inspire other people by your own cheerfulness and confidence.