I agree that planning is essential, though it may look a bit different for the homeschool instructor than the classroom teacher.
Failing to plan is planning to fail! If we don't have solid plans going forward, it's easy to get off track. That being said, we must remember that we own the planning tools- they don't own us. Especially in the home setting, but even in the classroom refusal to deviate from plan at times can add up to wasted learning opportunities.
More importantly, it's often the unexpected moments that cultivate loves and virtues. And if the plan nook is what we cling to, instead of the learning opportunities, then students will grow to be planners, not explorers.