Lots of writers, even the most famous ones, advocate that if you're a writer you ought to be doing it every day. It's a good way to exercise your creativity, they say, and how else can you get finished with a book otherwise? Should you be writing every day?
Habits, Hobbies and Obsessions
I found a quote online where even Mark Twain himself advised writers to writer every day. Easy for him to say, right? Writers in the 1800s didn't have to think about tweeting, or blogging, or checking their own sales figures. It may come as a surprise to know that Mark Twain self-published, but you can bet he wasn't spending an hour wading through emails every day or digging through book blogs to find reviewers. And then there's the fact that Mark Twain became pretty famous in his own time, and his books sold quite well.
So naturally, Twain had time to write every day because he was getting paid to write books. Lots of self-published authors aren't getting paid (at least, not enough), and that means they've got to get paid for doing something else.
By some standards, that means you ought to work a full day on the job, come home and then write. Every day. It's just not practical advice by any stretch of the imagination. Self-publishing is hard. Don't make it harder on yourself by wearing yourself out. Fatigue isn't going to help your creativity. For most people, it has the opposite effect.
Setting daily goals is a good way to maintain discipline, but you can also make yourself crazy. If you've got time to write every day, good! But if you don't, there's nothing wrong with making a decision to write on the weekends, on on Tuesdays and Thursdays, or whenever it fits into your schedule. When you reach Mark Twain status, then yes you should write every day. But when you're working multiple jobs, trying to establish yourself as a writer and logging onto Twitter all the time to boot, writing every day is a huge burden.
Don't turn writing into a chore, because that could affect your love of writing very negatively. If you're making yourself write, you're not going to be producing your best writing.