I'll totally echo a lot of the sentiments above. The first thing that have to know is that you have control over your schedule. Set yourself up for success.
If you have to publish only one page a week, or one page every two weeks, that's okay.
If you need to build time into your weekly schedule to get organized and keep yourself on track, that's okay. Google Cal is great.
I work about 30 hours a week right now. When I first started doing comics, I was working 40 hours a week. I'm making enough money from comics to cut out 10 hours a week of regular work and add 20 hours a week of working on/promoting my comics. My goal is to cut it down to 0 hours of regular work and work 50 hours a week on comics. Ultimately, it's about money and what type of job you have.
My primary source of income right now, as I've taken a break from performing to focus on comics, is bartending. Man, bartending is great -- it offers such a flexible schedule, gets you active and out of the house and social. I work two 15 hour days, Weds/Thurs. That leaves me pretty wiped on Friday, which I generally take off from doing anything more meaningful than updating pages. That gives me Saturday through Tuesday to write, promote and plan.
It's still not enough time. I'm constantly busy, but it's in a good way!
The old adage is true: time is money. If you can find a way to monetize your comics and work towards that, you can free up more of your time to spend on doing even more comic work. So, in summary:
Figure out your path to monetization, unless you just want to do it for fun. If that's the case, then don't worry about not always being able to keep up on your schedule! You're giving the world your stories for free; it can wait a few extra days if you need some well-deserved R&R.
Make your schedule work for your situation. If that means publishing less often, but always hitting your deadlines, and building towards being able to publish more as you earn more ... great!
Be happy and choose joy, always. If there's something about your schedule, work, life, or comic that isn't joyful ... make changes. At the end of the day, we only get one life and we all deserve for it to be a happy life. And, most of the time, it just comes down to us making the right choice for ourselves. : )