Balance is essential to staying sane while doing plenty. My plate: I run a preschool from my home during the school year; I have a three year old son, a husband and cat who all want a little something from me; and I'm working on a parenting book. My summer projects are (currently) keeping up the vegetable garden and prolific berry bushes, prepping our kitchen for painting (which involves scraping off layer-upon-layer of the Ugliest Wallpapers of Several Decades), working on parent handout/letters prior to preschool and planning curriculum.
Not a lot of time for *my* writing, so this forum (while sans pro editor) keeps me fresh.
Balance, for me, comes in various forms. Mostly it's about reading the emotional weather report at the beginning of the day and moving along with what my son and I need to stay happy (with each other and ourselves). Some days, we need some outings and other days, we stay home. Child care is a godsend, and I firmly know that I would be a mess without having those blocks of time (about 4 hours a week, usually) to get some chunks of work done. Some days, I forgive myself for letting him watch two episodes of Mr. Rogers, back-to-back, while I get just a bit more work done. Taking walks and getting exercise is essential, as are playdates and other social activities.
I also have learned what to let go of. At present, while the preschool is out for summer, I've let some housework go. Laundry will eventually be folded or worn before the week is out. (We have laundry-folding parties on the weekend if need be. 3 yo's can be overly-helpful.) Dishes and kitchen, however, are kept up. I let go of asking my son to nap for that mid-day break, and now he goes to bed at 7om. I'm learning to Stop Working by this time of evening and relax, which was a bit difficult at first. My husband then has more of my attention, which improves our communication and prevents more of those sorts of misunderstandings that can make us upset with each other.
Besides getting rest and trying to eat well, I would say my biggest asset is that I have surrounded myself with people who are supportive. There will always be others who question or criticize aspects of our person--how we parent, what sorts of priorities we have, etc. -- and I feel better when I'm around people who understand that we are all doing the best we can. The prissy people, who seem to need to make me feel that I am not keeping up my house/my looks/my parenting, etc. can really go take a walk. Supportive people can laugh at the mess with me and then have fun. That's what being a friend is about.
Time is my biggest challenge. If summer were twice as long, and if I had oodles of money to spend on childcare, all of this would feel more relaxed. Or maybe not. Acceptance of one's situation is important--all the good and the bad-- and when we can accept what it is that we have, it's easier to move forward and try to stay sane with the myriad demands thrown our way (including from myself). At least, it is for me.
One last thing--if you are a writer, you are a writer. Is it that you are aspiring to be published? Most of us writers are, to some degree. If you can, find a writing group or some sort of support. It's lonely work when we only have our children to read to, but even then--oh, if I couldn't write, I don't know what I would do. My head would explode. Take yourself and this work seriously, because this is a great topic to expore. Keep writing!