I am obsessed with planning but I am not obsessed with keeping to a set itinerary.  I research and try to retain info and tips on things we'd like to see and do. For the *must see or do's* I will research and prepare extensively so I can be sure we will get to do them during the trip. Other things, I don't stress too much about.   I make a list of priorities and make necessary reservations, etc.  I find out about showtimes and try to see as much a possible.  Key is to have fun, and for us, that's meant making the necessary preparations, but not trying so hard to adhere to a schedule planned down to the very last minute.  I guess it also depends on how much time you have and crowds.  If I were going during a busier time or going for less days, I'd probably be stricter with the planning and schedules.