Feeling inferior to other people is a typical thought of a S.A.D. person. I used to have the same feeling when I was in that nightmare. As S.A.D. person, we need other people's friendship so much that we cannot afford to lose it. So we do our best to please others everyday and hope they will be happy with us and continue to be our friends. We reply on the happiness of others and don't care about that of ourselves and gradually we develop the feeling of inferior.

We are trapped in this vicious circle :
Social anxiety -> lose friends -> need friends desperately -> ignore ourselves and feel inferior -> social anxiety

To jump out of this circle, we need to correct the irrational feeling of inferior and respect ourselves. Now cognitive behavior therapy can do this. Its process is very simple. In the cognitive therapy session, you keep telling yourself the positive message such as you are valuable and have the right to be yourself et. al. and your brain will begin to learn and accept it. Then in the behavior therapy, you show up in some social situations you felt anxious before to test what you have learned in the cognitive session, which will be testified and reinforce your new believes.

You can get the therapy at the psychologist or buy the audio series from the internet to learn by yourself.