The Velominati keep the rules. I am learning Rule #5 the hard way. Not exactly, lemme 'splain.
I am currently at school, in the middle of extreme productivity on the academics front. It is about twenty-to-six, and it is going to start getting dark in a little while. The dilemma: do I keep working so as not to interrupt the productive juices, or do I ride home now, while it's still light, recognizing that I likely won't do any work again until tomorrow when I get back to school at the earliest. Friends who know me well will immediately understand the problem: motivation and work ethic.
Allow me to spell it out: I don't work at home, unless I absolutely have to. Home is full of fluffy distractions, television, and food. Additionally, there's no guarantee that I will be flush with motivation tomorrow upon arriving back at school to pick up where I left off (in fact, my motivation at this present moment makes any tomorrow less likely: contact your bookie).
But, were I to finish this task, it will be after sundown. I will have to ride home in the dark (really, duskish twilight). I don't like it. I have lights, but not great ones. I have ridden later than this and, while it's not my favorite thing, it's not entirely unsafe and it is doable. I just don't prefer it.
Thus, this Urban Cyclist has come face-to-face with the urban cycling truth: it is sometimes inconvenient. Anyone who commutes by bicycle has come across this at some point, and it's not always productivity that gets in the way. Sometimes it's bad weather, sometimes it's being held up by others or eleventh-hour demands, sometimes it's traffic (but, honestly, what cyclist doesn't know how to avoid that?)
Your Urban Cyclist now has to weigh productivity and being that much closer to her degree (and present laziness, truth be told) with the comfort of riding the bike before dusk. Harden up, chick.