Hold up your hand. In the air, draw a figure eight with it. Feel your hand curve the surfaces of the eight. Is the eight standing up or is it on it's side like an infinity sign? Is the back of the hand feeling the path or the palm of the hand? Are you using your left hand or right hand?
Continue moving the hand smoothly through the air, as if nothing else mattered in the world, but relaxing the hand and moving it slowly. Don't think. Feel. As you continue, do you feel your shoulder? Is it becoming tense? Can you relax it more? Can you move your position, continuing the hand movement, and become more relaxed in the shoulder?
Are there parts of the taiji form you practice that are uncomfortable? Can you shift your body to make them feel less tense?