Dear Aditya,
I understand what you are going through, my advice is to relax for today and start pondering from tomorrow onwards, with peaceful mind.
The fact that you scored 700+ in both the GMAT prep's shows that its in you and you can make it to 750+. Today was not your day... thts it... it happens sometime... but I am sure you will crack in your another attempt of killing the beast.
May be its blessing in disguise, as you have more time for your preprations, as it will give you opportunity to score even higher.
and 670 is not a bad score to be disappointed pal...
cheer up... your day is not too far...
regards,
Amardeep