dispatches: Busy not making masterpieces:

I photograph every day. I don't go out with the intention of making a masterpiece every day. Most of what I do is process, not product. I do it to keep my eye limber, and to stay conscious of my ordinary, everyday rhythm and routine. I do it to remind myself that the special moments "worth" photographing occur only because you devote your attention to seeing them.

That's the discipline - get out there, do the work, do your time. Take lots of photos, but don't just rattle them off - take them right, pay attention, and actually work at it. The best ones you take will be a combination of you, and the moment - you spend your time practicing for that moment, so you're ready, so you can make the most of it. You spend your time training yourself, both your ability with your tools and your ability to see what's around you, to make the most of both together.