Listen to your body at a deeper level. It tells you when you're tired. Do not let your mind tell you that you have to keep working/thinking or... some bad thing will happen. That's what the mind will always tell you. What does your body tell you? The only way to know is to stop, take a few deep breaths, and check in. If you're really tired, listen to that. Sleep is more important than that last line of code. Your body has an incredible intelligence that our culture no longer honors.
If you're a night person, honor that by setting the expectation at work that you'll come in later and stay later. My mind is completely foggy in the morning, and completely clear in the evening/night. My natural rhythm (when I get to do it) is to be awake until about 4:00 AM and sleep until around 12:00 PM. I let the first part of the day go by, and then work in the second part when my mind is far more clear, right until before I sleep. My best work frequently happens between 10:00 PM and 3:00 AM. When I hear about people waking up at 4:00 AM, I think, good for you, but that's not a universal prescription (look up the word "chronotype").
If you're a night person, honor that by setting the expectation at work that you'll come in later and stay later. My mind is completely foggy in the morning, and completely clear in the evening/night. My natural rhythm (when I get to do it) is to be awake until about 4:00 AM and sleep until around 12:00 PM. I let the first part of the day go by, and then work in the second part when my mind is far more clear, right until before I sleep. My best work frequently happens between 10:00 PM and 3:00 AM. When I hear about people waking up at 4:00 AM, I think, good for you, but that's not a universal prescription (look up the word "chronotype").