Often people view planning as cumbersome, and then feel stressed (and like the planning itself was a waste) if they can't stick to the plan.
I view planning as 1) time-saving in the long run and 2) freedom.
On the first point, if you spend 10 minutes today planning out what you need to do tomorrow, or 30 minutes this weekend planning out your week, you are going to save hours over the following day or week. While planning, you are thinking about all the things you need to do once and prioritizing appropriately. Then you are able to spend the next day or the next week executing instead of thinking over and over about what you need do to.
However, I think the more important point I want to make here is that having a plan can actually provide freedom...as long as you view your plan as a (flexible) guide instead of a (task) master. A plan provides freedom from anxiety (because you know what you need to do), freedom from time-wasting (because you spend your time acting instead of rehashing), and freedom from overthinking (because you've freed up your brain-space by putting everything you need to do in your plan).
Here are a couple examples of how flexible planning can work to your advantage:
End of Day Work Day Planning
If you spend 10 minutes reviewing your task list and reprioritizing for the following day, when you start working the next day, you don't need to spend any time at all wondering what you should do first, or deciding what to work on; you've already prioritized. You hit the ground running.
Now, of course, things are going to come up during the day that were not part of your plan. But now you are able to take each item and determine whether it needs to be prioritized higher than what you had planned to do, or whether it should be prioritized for the future. Incoming tasks no longer need to derail you and you are better equipped to determine whether you need to repriortize your plan to accommodate them.
Weekly Meal Planning
Weekly meal planning saves tons of time, and allows you the freedom to never have to worry, at the end of a busy day, what to cook for dinner. By spending some time on the weekend making a rough plan and making sure you have the ingredients you need to execute your plan, you are able to simply cook at the end of the day.
And here's where the freedom part comes in: there's no reason you have to stick to the plan exactly. If you end up going out for dinner on Wednesday, just shift your plan by a day. But having a plan in the first place means you are never scrambling.