@Carol—I think that characters usually don’t realize that they’re doing something different until after they’ve done it (that’s when they do the one step back thing, reverting to their old ways), so it’s probably just fine to have the changes be very subtle in the middle of the story. Toward the end, however, I prefer to have a character make a conscious choice to change (even if s/he has no other options, they knowingly realize that this is something new and different).