Each moment of practice changes you. Each cut of the bokken, each movement of the feet, each fall that you take if done with serious intent to learn teaches you about yourself and the people you practice with.
...which, of course, is also true of what happens outside the dojo, although I'd change it to "each moment has the potential to change you". It's potential only, and the change may not be anything grand and trampling or anything tangible - it might be just a tiny shift in perspective or awareness. All the potential of these moments tends to get lost if you're focused on the Spiritual-with-a-capital-S experience.