Well I might not have classes and homework, but I've had some ups and downs to get in my way, particularly while I was drafting Silent Oath in the first place.
I usually get up between 5am and 6am, and get to sit down for the night after 8pm. In all, I've got my day job which, including commuting, takes up 11 hours of my day, Monday to Friday. I've got edits and promotion for the upcoming book. I have a weekly Dresden Files RPG campaign to run as well. A wife who's partially disabled and has to use a wheelchair or crutches to get around. And, of course, two 6 month old baby girls.
Somewhere in all that, I also write.
So I have an idea of how hard it is to fit writing in with a busy schedule.
I find what works best is to set aside a specific block of time to write, and treat that time as sacred, as though you're already published and it is literally your job to write in that time, even if you don't feel like it.