One must understand and use wisely, one's available energy reserves, based on how much there is to give in any one area, and still do an effective job. Or better, yet, to still live a fulfilling life. If you try to push too hard or too long in areas that aren't even your sweet spot, you will crash and burn. You might succeed for awhile. And it might be necessary to actually drive yourself more than is healthy for a certain amount of time. But don't make it a habit. You'll just die faster.