I mean, I only planned in the broadest sense, but I knew where this blog was headed for April, so I didn't have any issues with delivering the posts. Even though I didn't manage to schedule more than the first six or so days.
Life's a lot like that too. You don't have to plan every tiny detail, but having at least a vague idea of where you're headed helps a lot. It shows you what needs to be done. Also, it gives you an idea of when these things need to be done.
Also, knowing where you're headed is a lot like dangling a carrot in front of a donkey. Especially when that place is somewhere you want to be.
But if you don't know yet, don't force yourself to decide. That just opens you up to "helpful" outsiders who invariably give you bad advice that you'll follow, because you won't know it's bad until later.
And yes, I know this from experience. Much better to give yourself time to decide. And remember, once you decide on what you want, you don't have to lock yourself in. If you find yourself being miserable in something you thought you'd enjoy, change your destination and move on.
At least you would have learnt from the bad experience.
If you insist on staying just because you chose it, you're just making yourself miserable, and it's not what taking charge of your life is about.
So yes, it's okay to change where you're headed, as long as you're headed somewhere, and at least have a clue about where you want to be.
Did you ever choose to do something and end up hating it? Did you move on or did you stay? How did it work out for you?