There's a myth out there that women can multi-task and men can't. I guess like a lot of generalisations it's true for some people, but not others. It's definitely not true for me.
I can multi-task the simple things that don't need my full concentration, but when it comes to important, or more intense activities, I have to focus on that one thing.
I'm envious of writers who talk about working on numerous projects at the same time, though I sometimes have less than generous thoughts of whether they're actually working on them all at the same time, which usually leads to random thoughts of a line of computers with a writer dashing madly between them.
I'm able to switch between a non-fiction (paying work) project, and a novel, but nothing more than that. In much the same way I read one novel at a time.
Over the years I've been writing I've finally learned not to be so envious of someone else's talent, or way or working, and go with what works best for me.
I have a three-quarters complete first draft of another novel, which I started working on while I was waiting to hear from publishers/agents about Lives Interrupted. I'm eager to get back into it, but also mindful not to get too ahead of myself before Lives Interrupted is completely finished.
When I started Lives Interrupted the manuscript didn't seem to move along very fast, working on it evenings and weekends.
When my job finished I decided to work for myself, but gave myself three months off to finish the first draft. I worked on it full-time, and finished the first draft with a week or two to spare.
There is nothing like the relief and joy of getting to 'The End'. However good or bad it is, without that first draft you don't have anything to mould and improve, and I guess that's the point. Whether you can work on six things at the same time, or just one, it's not much use to you until it's finished.