Too many things to do

I always find it amazing that the more we need to do, the less we actually get done! I am sure that numerous books has been written about how to organise your tasks (as it is genericly called in this day of age) to that you make sure you get the most important ones done first and eventually all of them. But I don't find these tools work - and I am wondering if there isn't something fundamentally wrong in the way we decide our tasks. It seems like the more sparetime we have on our hands the more tasks we take on, but the less we get done. And I beleive it is this compulsion to fill all our time with doing stuff that is the problem; for some reason we can not accept idle time, so we fill it up. Problems then come when our non-spare time has become so stressed that we need the idle time to clear our heads. If we don't let the brain run idle once in a while, we just end up in the situation, where we get nothing planned or done and then we have the bad spiral where the tasks (some of them important!) just piles up and we are looking at the piles unable to react.