I've only been writing for three years. Two years before that, when I first gained an interest in screenwriting, I bought every book I could find on the craft of writing a screenplay and studied them like mad. Probably should have spent as much attention learning the craft of writing a winning query letter or logline, but for the moment that point is moot.
All three years I've been writing, I've been employed by a homeless shelter in various capacities as either a third shift case manager, a second shift shift-coordinator or, like now, as a Social Security program manager on first shift. Each of these jobs altered my schedule like crazy, and each, combined with my personal life, provided me very little time to sit and write at length.
But I made the time. Whether it was during my one hour lunch break, or leaving early a day or two a week (luckily I've always been on salary so I can get away with it). In the last six months or so, however, I've been able to omit anything unnecessary in my life and have found a world of open time. As is, I can still spend time with my mom and sisters, spend hours talking on the phone to my daughter in Canada, spend all kinds of quality time with my girlfriend, put in a full work day and still have about two hours a day to write, more on Saturdays and Sundays.
If you filter through all this nonsense (pardon me, I tend to ramble) you'll see the point I'm trying to make is that if you're serious about wanting to be a screenwriter, the by God you need to MAKE the time. If you don't, you're just kidding yourself. You didn't REALLY want to be a screenwriter. It just sounded cool for a while, an interesting thing to do since basketball season was over or maybe you just got bored and thought, "Oh, what the hell, it's better than mowing the grass." But if you're totally serious and committed to being a screenwriter...make the time. It really is as simple as that. And all hyperbole aside, if I can make the time, anybody can.