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I'm the same way, I love to overplan. Everyone isn't like us though. Some people thrive on just figuring it out as they go along and can make that work for them.
I would guess that planning helps improve your chance of succeeding but as many have said, you don't need to plan ahead, you can figure it out as you go along.
Something else to consider is how quickly plans/intentions change once you are out there. You could be saving yourself a lot of time by not formulating a plan that goes out the window on the second day.