Working on form is tedious and critical. It takes concentration to make microscopic changes that can lead to tremendous gains, so you will naturally slow down as you hone your form. Focus on how your feet are landing, the pace of your breath or how your arms are swinging. For example, if your arms cross in front of your body when you run, practice swinging your elbows directly back. If you notice your stomach is sticking out when you run or you have lower back pain afterwards, focus on engaging your abdominals.