Before one can truly appreciate the company of others, one must be able to appreciate their own company, to be comfortable with themselves, to love themselves.
Take a long look into a mirror, think upon the things that cause you this self doubt, what are they, the causes...
Remember everyone puts their pants on one leg at a time, no one is perfect, regardless of what you may have thought. Keeping this in mind, embrace your flaws, learn to look at yourself with respect.
Also remember,
We are all connected, never alone upon this round spinning sphere of energy!