Ever since I was a child I've been a night owl, and had a hell of a time waking up. In fact, mornings are sort of hell on Earth for me. Just wired that way. Anyway, I was in Vegas with my wife on a buying trip for her store last week, and because our flight was delayed we arrived late and the room-type we booked was maxed for capacity so we got an upgrade to a nice corner-suite, with floor to ceiling windows on two walls, overlooking the Vegas Strip and the mountains of Nevada. It was such a nice view that we just slept with the windows bare, and in the morning, the Sun rose sometime before 7am, flooding the room with a warm glow that turned brilliant as 7 approached. HOLY SHIT was it easy to wake up there. All that natural light just did something to my brain...I had to get up earlier there than normal, but I never had to use an alarm (I can find a snooze button from 300 yards in the dark normally). It was the most soothing, gentle, yet irrefutable call to wake I've ever experienced. Sort of bummed that I'm back in my soothing womb-cave.
I once subletted my room to a friend while I did a study abroad and when I came back, she'd painted the room bright orange. She also took the window shades when she moved out, or else I'd forgotten that there weren't any on the windows. Anyway, nothing like crashing after a late bar shift and then several hours later, having to make the decision to leave the room or go blind.