I think personally (and I'm sure it has already been said) that the time you devote to writing is just as varying as anything else. People who are devoted to their craft and are able to write every single day have earned my respect. However, writing every single day just isn't for me. I don't think that people who write every day are socially deprived, ignorant or even gluttons for punishment. XD I think they just have a higher dedication to writing. People have varying priorities, things that are more important to them than other things. But if someone doesn't write everyday and they are published and successful, we shouldn't hold that against them and say, "They just don't know their craft!". It is sort of like being prejudiced. "Oh well, they don't write every day, I don't want to read their books." or "Well how do they expect to get published if they don't write every day?".
At any rate, I don't write every day simply because there are times when my home life demands more attention. Then there are days that, after writing for a while, I need to stop and hammer out some details. Sometimes I need to stop thinking about it all together for it to work out for me. If I stress about it too much, I worry myself into a frenzy and then I stop writing for long periods of time.
I believe you should set your own writing pace. Sometimes if you try to emulate someone else in your field, you'll feel even worse if you somehow don't live up to their standards.