Don't feel discouraged! You went out and rode, and that's what counts. Sometimes I go out with the intention of it being a long or harder ride, but my body just doesn't have it. All you can do is change up the gameplan and decide that's a day to enjoy the scenery. I bet you would have felt worse if you'd done nothing at all.

Like you, I got up early, but decided to bike to work. I'm terrible at morning rides, and my HR showed it! Maxed out up the two big hills, but my legs never stopped moving. Average speed was down, too, even though I felt like I was moving well on the flats. Temperature was perfect, I hope it's not sweltering this afternoon. 9.5 in, about 10mi back to home.