One of possible drawbacks of a flexible schedule is that your sleeping habits can go completely crazy. I've been trying to make them more normal later, which meant I didn't have enough sleep last night and really slogged through the day... and through riding. It's kind of nice to slow down sometimes though, but feels weird when so many other cyclists are passing you. I did turn it up a couple of notches at the end of the ride home though, to keep up with auto traffic where it made good sense.