Despite being a night owl, I find when I'm up and about at sunrise1 I feel mentally much better than any other time of day - regardless of how much sleep I've had or whether I've been awake for many hours prior to sunrise. Indeed I'd almost imagine getting up for dawn and then going back to bed would be beneficial in and of itself.
Why is sunrise therapeutic?
And are there reasons above and beyond the circadian rhythm2?
1. Strictly speaking, nautical twilight
2. Since the psychological effect of sunrise can apply even when jet lagged or are so frequently a night owl that prior reinforcement of experience is unlikely.