Daniel Pink argues you should test your routines like a scientist tests hypotheses. He started work at 7 AM, found it didn't work, and switched to 8–8:30 AM. Since everyone's different, the only way to find what works is to experiment and adjust.
One of the things that we don't do enough of in our own lives is act like scientists. What do scientists do? Scientists have hypotheses and they test them. So I could have a hypothesis saying, and I've tried this, like, okay, great, my peak is in the morning, maybe I should start work at 7:00 AM. That doesn't work very well for me. I'm not actually quite awake at 7:00 AM. I can wake up at about 7:00 AM, but my brain doesn't really activate until about 8:00. So I had a hypothesis, I should start at 7:00. Doesn't work very well. For me, starting at 8:00, 8:30, that works very well. And that's it. So we all wanna have, Uniform, one-size-fits-all answers. And human beings have variation, and we're not all— we're not all identical. We have small variations here. And what you want to do is you want to test it.
