Many times we expend a lot of energy trying to reach a goal. Working towards a goal is admirable. Pushing yourself to exhaustion, however, is not healthy. You need to assess how much energy is needed and determine what your limits are.
I have found that I am the most efficient when I am well rested. You are more apt to make mistakes when you are tired. Mistakes can result in hurting yourself and others. You need to be well rested to be at your best physical and mental shape. Well rested individuals are more likely to complete tasks successfully.
When you are tired you are more likely to get sick, too. Recovering from illnesses prevents you from accomplishing your goals in a timely fashion. Sleeping is essential for all of us. Finding time during the day to relax is also important. It is vital that you accept little gets done when you are tired.