Stand in a comfortable distance from your partner and place one fist on him and lean on the fist. Your partner will move in place to remove the pressure and both learn how to move so the strike slides off you if you cannot move away or have to stop the hit. Next do the same drill when the partner moves slowly to hit and you move to slide him off upon contact. Slowly increase the hits and remember to keep breathing. Work from all angles and sides and later on try to work with eyes closed and using the ends of a stick.
If you cannot or must not move from where you are, you can still gain some relaxation and alignment in movement by lifting one leg off the ground by a little or walking in place.