As far as I know, supreme court justice will not enter your house and forcibly get you married off to your cousin. This judgement will have no effect on anybody's life - so relax and don't get your panties in a bunch.
The court came to this decision because in the Indian penal code you cannot marry your biological sister. A woman from the same gotra who is not born to your mother is not your biological sister. Don't come and pounce on me for clarifying things ... and keep your hyperbole to yourself.