I plan. Ok, understatement... I plan a lot!
I think the planning is what makes me love the vacation - I build it up in my mind and it makes the winter months less dull thinking about Disney. The first time we went, I thought we would be one and done, so I crammed in too much. It was a blast and we saw it all, but it was busy and there wasn't much spontaneity. I got bit by the Disney bug on that trip, and we've been back every year since. I swear the planning is what I found so addictive.
Now, I don't feel quite as manic about it. I make my ADRs (usually just one per day), and get our FP+ for the rides we want most, but knowing we'll be back allows me to breathe. Our most recent trip was so different, because we didn't speed walk all day, we sauntered and shopped, and chatted with cast members. The whole family felt a happy difference in our pace, but that's because we didn't feel the need to see it all.
Our next trip is probably our first/only trip during the holidays (at least until I retire or hit Mega Millions), so I am scheduling us up again, but if we're going to see all the fun holiday things, I feel I need a plan to follow. I hate feeling like I missed something.
I think: find the balance that works for your family, be open to some breathing room when you can - even if it's just a few late afternoon park hours that are left "open for exploring" but be sure you make a list of things you don't want to miss out on, so you can leave with no regrets - if they are even possible at Disney!