Biorhythmic Writing? A Method, or an Excuse?

I do not get up at 4:00 AM to write. I hear about writers who do (quite often, in fact), but I've never been up at that hour to witness such a feat.

I don't write at 2:00 or so in the afternoon. That's nap time, and I'll end up face forward in my keyboard. I'm not saying I actually nap--but my body drags and my mind goes blank and my fingers go slack at 2:00PM.

My best hours are about 6:45-10a and 7-9p. Unfortunately, my body is most up for a good sit-down while I'm pushing the Stevens-sons out the door, teaching my morning fitness classes for the day job or eating dinner.

So what do you when your writing and the flow of your life conflict? How do you harness the energy from 8:00AM to use it at one in the afternoon or even three in the morning?

Do you change your schedule, or do you power through?

(And pardon me, do, if this post is slightly incoherent. It's 2:27PM and my over-long acrylic nails keep tapping the wrong keys).