Rest.

 Let me tell you that when your body tells you that you are tired, it is much better to listen to it is to try and be a superhero only to prove a point to yourself. You'll be more tired by the end of the activity and it will take you longer to recover from that. That's how it works. Fatigue is real and no matter how tough and strong you think you are, your body will fold, and it will fold with or without your permission. Our bodies are organs that need a lot of different sources of energy. It also needs sufficient rest. There is no point in sleeping only for four hours day trying to be productive, you will achieve the opposite of productivity. That is not what you want or are trying to accomplish, I am sure. There is no point in working out for 4 hours day if it means you feel like you're about faint or even die. That's the exact opposite of trying to be healthy. Understand your body, understand your mind. Give it what it needs and the respect that you know it deserves. And most of all, don't mistake this for asking you to be lazy. You know who you are. 

Love, peace. 
An Earthian.