Why is my blood sugar still unstable even when I eat well and exercise regularly?

I have seen so many people on here say the same thing: they eat reasonable meals, they walk or work out most days, they sleep okay — and their fasting sugar is still all over the place, their post-meal numbers still spike for no obvious reason.
I used to think it was just about calories and carbs. But over time, I have noticed two other things that move the needle almost as much as what you put on your plate:
1. Chronic low-grade stress. When you are constantly running from one task to the next, never fully winding down, your cortisol stays elevated all day. Cortisol tells your liver to release extra glucose, even if you have not eaten anything. That is why people will say "I ate perfectly today, why is my sugar 180 out of nowhere?" — half the time, it is the stress.
2. Poor or broken sleep. One bad night of sleep can raise your insulin sensitivity by 15-20% the next day, no matter how perfectly you eat. Your body repairs its metabolic balance while you sleep. If you are only getting 5-6 hours a night, that repair never happens.
I am not saying food and movement do not matter — they are the foundation. But if you have those two locked in and your numbers still feel random, look at the stress and sleep first. It is never just the plate.