If you want to be an entrepreneur it's not a job it's a lifestyle. It defines you. Forget about vacations about going home at 6 pm - last thing at night you'll send emails first thing in the morning you'll read emails and you'll wake up in the middle of the night. But it's hugely rewarding as you're fulfilling something for yourself.
I started writing when I had three kids under the age of 4. I used to write every ten minutes I got to sit in front of a computer. Now when I have more time I function the same way: if it's writing time I write.