It's tempting not to bother with planning, because our time is so limited, and our bosses really call the shots, and goals and priorities change so often. Those sound like good reasons, but there are also plenty of good reasons to plan anyway, even when you're "sure" it won't do any good.
Here are a few to consider:
Planning organizes you. The planning process forces you to think--to analyze what should be done, what the priorities are, how major projects might be handled. Even if your plans are never put into effect, the process of making them will help you organize your thinking about your work and your team.
Planning improves future decision making. The planning process involves dozens, sometimes hundreds, of decisions. As you make each one, you consider alternatives, risks, costs, and potential rewards. Later on, when the impact of the decisions you make becomes clear, the memory of those considerations and the way you handled them will serve as a guide to better analysis, anticipation of consequences, and decision making.
Planning helps you prevent some problems and solve others. Even when no other part of a plan is used, a listing of real and potential problems--usually an early step in any planning process--will be. Even though the priorities and goals that you choose may be changed by someone else, the problems will still be there, and you'll still need to do something about them.
Planning works even when it's flawed or incomplete. The process doesn't have to be perfect to be helpful. The lessons it teaches can be learned just as well from poor plans as from good ones. In fact, poor plans tend to offer more learning opportunities than good ones do. Plus, as soon as any plan is made, those involved in making it begin to refine it. That means no plan is ever finished, and no plan, however faulty or incomplete, is useless. It will always give you a place to start and a sense of direction.