A friend of mine asked me if it was rubbish having a toddler and trying to write. She asked via twitter so I tried to write a pithy 160 character reply. But I failed because there are two sides to this story:
Yep, it's difficult. Cyril Connolly once said "There is no more somber enemy of good art than the pram in the hall.". And certainly kids demolish time, there's no doubt about that. Weekends are swallowed wholesale, evenings eroded, energy leeched, patience tried. There is almost no time to get ahead in any meaningful way beyond turning up for work (I now call work 'rest') and doing the basics.
So answer one, yes, it is rubbish if you want to devote the entire length of your day and life to writing.
Children are sponges, they pick up on your energy. You have to actually be happy around children - not jolly, or 100% nice all the time - but happy. And for me part of being happy is writing. And the other thing that gets you as a parent is that you suddenly want to be successful. Not in the 'My bonus is bigger than your bonus' way, but in the 'I gave it my best' way.
So I get up at 6am and write for 90 minutes on weekdays. Some call that discipline, I call it necessity - for me and for Baxter: He needs a happy Dad, happy dad needs to write!
Luckily I don't need a lot of time - I am one of those writers who works very quickly, has lots of ideas and can achieve something useful in 90 minutes. Also screen/stage plays are quite short by literary standards, mostly short of 25,000 words, so once you have figured out what the hell is going on I am can crank out a draft in 4-6 weeks.
BB (Before Baxter) but still with a fulltime job this used to be about 3-4 weeks, so things are slower, but because of the need to be happy and successful my writing is better, more focussed and more enjoyable.