We clutter our minds with vague promises about what we should do, what we could do. But there is always more to do than there is time to do it. Most of the stress that people feel doesn't come from having too much to do - it comes from not keeping agreements they've made with themselves. When you tell yourself you ought to do something and then don't do it, you experience self-doubt and frustration. You can fool all of the people some of the time, but you can't fool yourself for a second.
Productivity is about completion.
It sounds simple. They think far too much. There's usually an inverse relationship between how much something is on your mind and how much you're actually doing about it. If so, you're wasting your creative energy. You've got to get that item off your mind.