As others mentioned, I also get up early. Like to write before I start my day. But for me, I would rather write than do anything else. I force myself away from the computer to go to work, or to get things done around the house.
My three children are grown and out of the house, so it is much easier now, than when they were home and younger. Then many times I would stay up till after midnight. I'm one of those lucky ppl that don't need alot of sleep (kinda find it a waste of time...lol) Also as I've mentioned before, for many years my husband and I owned restaurants and clubs, so being up after midnight comes with the territory....Now, life is much quieter, as we own liquor stores, with regular hours, and much less headache.
But writing is my first love, something I need to do. Like Janet mentioned, I too will think of things in bed or while doing something else and either jot them down, or make notes in my phone. I write or revise almost every day.....
Also totally agree with Allen. You don't need a lot of free time to write, you just need the drive. Sometimes too much time is a deficit. Altho living in the NYC area, I am looking forward to a forecasted snowstorm this week and some time at home writing....