Biggest Mistake in Organizing

I was recently asked the question, "what's the biggest mistake you see with people you're working with?" I had to think about it for a minute, but quickly decided that absolutely-it would be when people don't have a plan for their day. What I mean by this is, too often, people walk into their office, and simply open up email and let whatever fun surprises are in the inbox, direct their entire day. Yes, maybe there are one or two things people know they need to do, but so often, it seems that people are too casual with their time. And trust me, I'm not a naturally disciplined or detailed person, but I do know the importance of walking into my work day with a purpose- a mission to accomplish x, y and z... If we don't decide how we want to use our time, someone else will decide for us. Would you let someone else make all your decisions on how you're going to spend your money? Of course not! Your time is the same way- it's hugely valuable, so you must have a plan for it, each day. Obviously, we all have fires that come up, and we all have to readjust our priorities based on what the day presents us, (some industries much worse than others), but if we aren't consciously choosing how to use our time, it will disappear wastefully, leaving us wondering at the end of our day, week, year, or life- where did it all go?!