Stepping in Taiji is always fraught, though it appears not so. Lifting the leg, then extending it to its new position, requires tension in the hips to hold it all together, which means, despite the best intentions, your energy rises a little. So, on placing the foot the first thing to do is relax back into the weighted leg, the one you're moving from, then visualize the pathway through the arch of the legs that your weight needs to travel to get to the other foot, and either throw your body with the weighted leg or pull your body with the leg that has just stepped, along that pathway. There should be the sense that the journey from one foot to the other has come from one sudden explosion of effort which has been stretched into duration. Leap from foot to foot, but drag it out. This our resistance.