I'm kinda in the same "planning boat" with you (and a fair amount of people on these forums)! I tend to get sidetracked while doing my household activities...for example: laundry. A month or more before a trip, I find that while I'm folding/hanging clothes (which is at least 3 times a week), I'll pause and say, "Hmm, I think this would be a good outfit for _____ to wear down in WDW." Then, I grab an empty basket and start "packing" our outfits! An hour will go by...this happens once a week...and will happen again today as I fold/hang my laundry! About a week before our trip, I'll finalize said outfits and force myself to remove a fair amount of clothes, because I know I'll have access to a washer/dryer and will probably do a small load every other day.
As for making "lists," I'm right there with you. Lists provide structure for planners like us! However, I find that once I'm in WDW, I become more flexible and my "lists" become more or less mental check boxes. If I don't get to check off all the boxes or check them off in a different order, I really don't care, because I'm in Disney World after all! I find the more I plan beforehand, the more I can relax while actually there! There will be little-to-no guessing, "which park should we visit today?" or "where should we eat for lunch?" because my "lists" will provide me with ideas and possibilities!
Oh, the joys of planning and re-planning! BTW, my countdown is at 16 days and I am getting more and more excited!