For example if you are pushed backwards with a foot, go back and let your own knee rise and hit him in the back of the knee or add a roll to the side with the raised knee and roll him facing down so you can run away or work otherwise.
Remember to move the least possible and to start the movement as the body moves and that you have more than hands and feet. lead with your elbows and knees from time to time to discover new ways you have in you and if you are spread in your entire body you will have much less open doors for another to walk in through. The relaxation that will come from this will allow you in turn to see others as people and to see them as they are human and thus with many many flaws and tensions that we can use to stay alive if they choose to hit us.