Anything that's worth doing is worth working at. I've said it many times, and I'll say it again.
Yesterday I worked my day-job, and it took way longer than I expected. I worked hard, and today I'm exhausted, but it was satisfying! I accomplished something, and even though I didn't get any writing done, I still felt productive. I did something that matters to me.
Today I have to work the day job again...except it will be at night...at 9pm until I get done. Then I have to get up and start at 8:30 tomorrow morning. I KNOW I'm going to be exhausted by the end of this week, but this is one of the better weeks I've had in a long time.
I think this is something that aspiring writers need to keep in mind, especially if they're working another job. Take satisfaction in ALL of your accomplishments. Enjoy the moments when you do something well. That way, when you get a rejection letter, or go several weeks without hearing from the dozens of agents you've queries, you'll still have a reason to keep trying. And you won't get too depressed.
Now I'm off to watch Buffy while I work on writing stuff.