I used to be one of those people who would boast of how little sleep I needed, frequently working till 2-3am and waking up before 6/7am. Now however, I seriously evangelize against it even where I'm not paid to do so. I can only say sorry for the number of deadlines I missed and the errors in my work that my bosses and colleagues had to deal with.
If you compromise your sleep or diet, you can come to work be at your desk between 9 - 5, but because your are chronically tired, you might as well be home. There are times when we have to spend our time outside of work to do more work to sustain ourselves, this is perfectly understandable and even necessary but should never be allowed to compromise the quality of the work we have promised to deliver.
As a biological organism, your brain prioritizes your safety, so especially for those of us doing intellectual work, your productivity for some 'employer' is not your brain's first priority from a biological point of view. To be creative requires your brain to dedicate resources and processing power to the tasks you are engaged in. Your brain cannot think creatively to come up with new ideas if you are chronically tired and malnourished.
As a side note, I believe many of the illnesses and sudden deaths you hear about, may not always have to do with witchcraft; too many people are running their bodies to the point that one small illness shuts the whole system down.
The reason this is hard for people to understand is that, God gave us very a strong machine called our body, it can sustain a lot of pressure and it will take a long time for it to snap under the pressure, even with very extreme lifestyles. Habits such as little sleep, too much caffeinated drinks (especially when we are on too little sleep - coffee, energy drinks etc), alcohol, smoking, eating junk food - the porsche food we buy.
The point is, your time outside of work determines to a great extent, how productive you will be when you are at work. Take care of your health - try to eat well (which is not the same as eat expensive), sleep well, keep healthy. Note that you can eat expensive food and still be deficient in essential nutrients your body needs to perform at its best.
Have a great end of week...