When I worked at a writing center, we often talked about how writers are either "eekers" or "gushers." Basically, you have the people who want outlines, note cards, and lots of structure when they write, and then you have the people who love brainstorming, mess making, freewriting as part of their process. There's nothing particularly wrong or right about either approach; they are just different.
Similarly, some yogis discover that they love the freedom and improvisation of flow yoga. Others like the regimentation and discipline of Ashtanga. Still other yogis appreciate the academic focus on detail that comes in Iyengar yoga. Again, no wrong, no right, it's all yoga.
As far as habit goes, there's certainly something to be said for knowing one's strengths and weakness and developing a routine that works. But sometimes, routine becomes, well, routine. And though it's comfortable, routines can get boring or stale.
Adding a little variation can remind the practitioner of the broader field--other ways of doing yoga, other ways of writing. I'm not suggesting we do this all the time, mind you, that might eliminate productive disciplinary expertise. But just a dash now and again might bring new insights, bring new flavor to the practices we've grown to know and love very well. Even if we hate the experiment, we gain new appreciation for our habits. And if we love the experiment, well that's just gravy.