I used to be the most organized, straight up, couldn't change my plans person there was.
I hated when my plans were not carried out, or when someone disrupted my time schedule. I always wanted things to go smoothly and perfectly. Anything that did not was extremely frustrating. It would upset me and ruin my day if it went wrong. Yup, I was that uptight.
It took some time, and some good friends, that made me realize that life isn't about schedules and timing and perfection. It was about enjoying every moment, being surprised what happens next, and just going with it.
So why is this important to me as a writer? I have never been a planned writer. I make my story up as I go along, BUT I still had this idea in my head of where I wanted my story to go. Then I would get stuck when I couldn't figure out how to get there. Also, I was not good at rewriting because that meant taking apart what I had created and do something different. Which meant I had to admit that my carefully laid plans (story) wasn't perfect and I was not going to admit that!
By learning to just go with it I have a much easier time writing stories. I have discovered that sometimes my stories don't end up at my pre-planned point B, but .... they end up at a really great point B elsewhere. I can rewrite and found that in so doing I can strengthen my characters and my novel. And most of all, I can take criticism and opinions when it comes to critiquing my story! This is very important to a writers, but a uptight person with plans cannot begin to handle those things.
It makes it very easy to see a critique returned that I may/may not agree with in any form, but by just going with it I can see a different point of view and it makes me think about my story. And that thinking and allowing for changes is what makes my writing better. I don't have to take their suggestions and if they don't like my story I can shrug and say "oh well, everyone else seems to like it - I guess I can't please them all"
I laugh now when things don't go according to plan. But I have more fun, I enjoy life and experience new things more often, and I believe my writing has greatly improved from learning to "Just go with it"