Just do it!
It's easy to find excuses as to why you don't have the time or the ability to write. I know, because I do it all the time. Sometimes, it seems it's far easier to make an excuse to not write than to actually write. Some of the excuses are valid, of course, but there are also usually ways to work around them. For instance, my excuse used to be work. I was working from 8am to 11pm at one job I had, five days per week, and then taking extra shifts on the weekend. When I was actually home, I was exhausted, eating or sleeping. Period. I think I snuck in some taped episodes of "X-Files" every little once in awhile on weekends. I started a novel during that time that just sort of fizzled out after one lovely evening of just writing. My husband left to go out while I was writing, and I was still sitting there knocking it out when he got home. Other than that, though, no time.
When could I have written? Well, I think this was a fairly valid reason not to write, but I could have found time on the weekends. I could have written during my lunch break.
Another of my big excuses was (and often still is) my children. They are 6 and 3. I worked through my pregnancy and attended college classes at night, so I was rarely home, and I was, again, exhausted when I was there. When my son came along, all my time and energy was invested in him. Plus, I was still doing college online. Every little once in awhile, my brain would spit out some ideas or I'd get a little inspiration, but I'd have to set aside any piddly writing I'd done in order to write a college paper or study for a test.
As he got older, and I had a second child (I graduated with my Associate's when I was 7 months pregnant with her), it became more work. When he was a baby, though, I kept saying I'd write when he got older, when it was easier, when he could play by himself.
I made those same excuses when she was a baby.
Then I said when he was in school and she was old enough to play by herself I'd write.
Then I said when she was in school I'd write.
Guess what? She's not in school, nor was she at all this year, yet I wrote a novel. A whole novel! It took me finally putting my foot down and saying, "Enough!" I had to decide that I would find a way to write. I had to decide that it was important, and it deserved planning. I had to make it a priority.
So my response to those who have excuses (not valid reasons, but excuses) is to just do it. Find a way. Make it a priority. You can't be an author if you never give yourself the time to write.
I figured I'd end this post with a quote that amused me, but that I also thought could be made to apply to many things, including writing. From "Princeps' Fury" by Jim Butcher:
"[...]in the course of my life, I have more than once been too ignorant to know that something was impossible before I did it anyway. I see no reason to jeopardize that success."
What are some of the excuses you've had not to write, and how did you get past them (or have you)?