If you are two people you can use the wall to effect the third person and if you are by yourself you can roll on uneven ground so your body will be free from the need to keep its form and location and be more aware of the tensions we use to remain in our state and current posture. Keep breathing.
Have a partner or two stand in a line and have the last one with the view of the others push the partner in front of him toward the third and the middle one being pushed needs to let the push go through him without hitting the third in front of him and cleaning himself from the fear of being hit from behind. You can change places and stand with the side to each other or facing each other and this drill is simple but deep in its learning. You can also push with your feet and entire body and you will find that a simple and small change to the position of the spine will make moving even a hard big fellow easy.