There is ALWAYS a reason not to write. Heck, there's always ten reason not to write. Even if you clear your entire life of other responsibilities and have nothing to do *but* write you can always find a reason not to. It becomes a question not of whether you have something "better" to do and more a question of whether or not you have the willpower to say "No, this half-hour a day is important to me, I need it to write in and I need to write, so STFU rest-of-the-world".

I need to take my own advice ... :P