Smile, it helps
To learn to move freely when you hit tense up the arm in a position where the tendons are strong (usually in the 90 degree of the elbow) and relax the shoulder. Now start to move the arm through the shoulder and work to keep it relaxed and find all the ways of movement you can. Work with both arms and have a friend hit your arms and push them with a stick so you find a way to escape and continue moving from the shoulder. Now relax the arm keeping the forearm and fist tenses and repeat the drill and than just with the fist tensed up. This makes you more aware of the tension already inside you and release it. Now move with a partner as your arms and shoulders are relaxed and close the distance if you can as he holds a stick and hits and pushes you with it. Keep moving and breathing and avoid keeping him at a safe distance. There is no safe distance. Choose what makes sense to do at that moment and remain calm. Many times in life and in the part of life you call class people will move much faster than you out of ego, out of fear and out of pure ability. Control your own speed and you will be able to survive and control others.