How do you balance flexible travel with booked Shinkansen tickets in Japan?

[LarryEM]

Okay, so we’re planning our first real trip to Japan and I keep hitting a wall with one thing. Everyone says you need to book the shinkansen tickets way in advance, but I’m the type of traveler who likes to keep things a little loose and change plans on a whim. Has anyone else tried to balance that bullet train schedule with wanting some spontaneity? I’m worried we’ll either be locked into a rigid route or stuck without tickets.