The simple step of letting natural light into your bedroom makes it a lot easier to wake up near dawn, which generally gives you quite a bit of unstructured time to prepare for the day. Of course the flip side is that you'll be a bit more tired in the evening and at night, but that also makes for a nice self-sustaining pattern. It's a good example of replacing self-enforced "discipline" with natural adaptation.
But leaving curtains open lets in too much light at night. Especially cities and suburbs which are never truly dark, but even in the country when the moon is bright.
Now I want to build an "alarm" that silently opens curtains...
It's still a great tradeoff. Even comparatively strong LED lights are generally a small fraction of the intensity of true natural light. You get used to it.
