I think it's more important to get into the writing habit. I don't write every day, but I find that when I'm not writing at all for a few days at a time my mood sours somewhat. I'm a firm adherent of Malcolm Gladwell's theory that it takes at least 10,000 hours of practice to get really good at something. That's a lot of writing. I have five novels I wrote in grad school and about 2 million words of fanfics that I posted on a gaming forum, before I started my "serious" writing (i.e., the stuff I've self-published over the last few years). I go back and look at those early novels sometimes in the hopes of being able to polish them up and publish them, but they're just too raw. But I would not have gotten to my current level without having written them.
There are gifted writers who just start out good, and can publish in their teens/early 20s, but I do believe that for most of us it does take years and years of work before you can really make it as a writer.