The current issue of The New Yorker has this interesting article on procrastination, which, appropriately, I just read instead of doing actual work I need to finish.
It seems to me that procrastination is rational to the extent we can’t be sure of future events. As uncertainty about future events increases, putting off preparations now for events far in the future begins to make sense. (If the problem might actually go away on its own, ignoring it for now many be the best strategy.) I suppose what has changed is that the modern world is a lot more predictable than the world of the past. It seems that our brains sometimes aren’t wired for a world in which events far into the future are actually pretty predictable, leading us to procrastinate on things like exams, papers, doing our taxes, and the like.