u are here demanding approval and acceptance from girls thats causing ur nervousness and when u dont get it u call urself worthless,no damn good , looser etc. thats completely irrational and unrealistic view. Understand rejection only shows her choice and has got nothing to do with what u are. In reality Your worth in the society remains same before and after rejection but its ur own self downing about it that causes u to fear it so u become nervous. Just feel free in approaching girls even if they reject u it wont harm ur worth actually and u will learn many good things from it that will help approach the next girl.