In the main set, you will be swimming progressively longer distances of freestyle. Your goal is to maintain your stroke count even as you swim greater distance. To hold your count as you fatigue, you need to hold on to good TECHNIQUE. To do this, choose a focus point. A good one is to simply HIDE YOUR HEAD. Another would be to STREAMLINE and get good distance off each wall. Another would be to HOLD ONTO the water as you pull. Choose whatever works best for you. Choose just one point and really focus on it.