When someone grabs you from behind.... -Remain Calm
Grab assailant's arm
Drop your weight
Stomp the assailant's foot *Do not drop your weight and stomp their foot at the same time. this will cause you to lose your balance.*
Then kick back towards the assailant towards the knee/groin area
Another option: Head butt the assailant after you drop your weight instead of stomping their foot.
Another Option: Bite the Assailant on the arm after you drop your weight.