You need a plan to get you from point A to point B, but also for the following purposes:
- To show your boss the path ahead
- To prioritize the numerous tasks ahead of you
- To communicate with Key Stakeholders to ensure that your tasks aligned with the Company's needs and that you have enough context to get started.
Plan just enough that you know what you need to do, but not so much that it would be painful to change the plan if something unexpected happens.