In order to accomplish something great; something truly worthwhile, your work must overcome you. You must lose yourself to it. It must become something which is more important — even than your own physical and psychological wellbeing.
Do not wonder that great artists so frequently overdose on drugs.
Do not wonder that missionaries go to areas of the world wrought with disease, violence and tyranny.
Do not wonder that you hear stories of soldiers losing limbs, only to fight to return to battle with their comrades.
Their work overcomes them. That is why they are great.