I'm not sure I'm qualified to answer this week's question. I can't compare the pleasures and pitfalls of writing full-time to those of writing part-time, because I've never been a full-time writer.
That's right, aspiring writers, it's reality-check time: I've got two books out, and a third following in a matter of weeks, and I still have a day job.
I can't complain. It keeps the light on. The fridge stocked. Thanks to the day job, my teeth won't fall out of my head, and if God forbid I step off the curb tomorrow and get run over by a bus, my medical bills will be (mostly) taken care of. That ain't always a given for full-time writers. (Nor, it should be noted, is it true for a lot of people who bust ass for a paycheck eighty hours a week, but that's a topic for another time, or perhaps for a letter to your congressperson.)
As for the downside... you ever hear about the frog and the pot of boiling water? Apparently, if you drop a frog in a pot of boiling water, he'll try to hop back out. But if you put a frog in a pot of cold water and then heat it to boiling, he'll stay put until he cooks. It seems frogs are unable to sense the gradual increase in temperature until it's too late. (I haven't tested this, for obvious reasons, and I couldn't bear the thought of Googling to find out if it's apocryphal or not. I'd like to continue believing it's made-up. Either way, suffice to say it's not easy being green.)
Writing while holding down a day job is like that. At first, it's no big thing: a couple hours on the weekends here and there. Then you make a short-story sale or two, and get a little busier. If you're very lucky, you land an agent and/or sell a novel, and you get busier still. Next thing you know, you're two books into a series and you've got six months to write the third, while also hitting up a convention or four, trying to sell a second series you've been noodling at in your spare (ha!) time, and oh yeah work family holidays eating sleeping when's the last time anybody cleaned this place I think that pizza box is moving AND OH DEAR LORD WE'RE OUT OF WINE .
Sorry. That got away from me a little. But you get the point.
Don't get me wrong: I signed on for this life, and I don't regret a second of it. That said, if any modern-day Medicis are reading this and feel like cutting a check so I can focus on my writing, shoot me an email and we'll talk...