In many cases people want to take you to the ground and stay standing. If you are already out of balance (they catch you when you are sliding on some ice or simply not paying attention to what is around you) you can go down and take them with you as you help yourself up and keep from harm. For example if someone reaches and tries the smell my armpit lock on you as he twists your body toward the ground you can simply relax down as you hold onto his belt or coat and roll so you land on him and continue to move without getting hurt or dirty by what he was aiming you to meet. Another example can be the choke from behind and most people try to fight the choke as it is unpleasent and we want to breath. Try to stay close to him and have him take the hit of the ground and stay in motion so as he impacts the ground you keep moving and escape the hold and now you are free to choose your actions. Practice.