Sometimes rethinking a problem or matter will gives us a better way of looking at them in a interesting way. We always want to have an outcome that is the most productive result at any given time. When we think about renewing our minds, we are revisiting the thought in a refreshed manner. When think about renewing our purpose, it isn't the action of not fulfilling our purpose, but more of restarting  our purpose in a way that is refreshing and different.