The Autofocus System is a popular productivity system by Mark Forster. The essence of it is that at each period of time you work on a single task you feel like doing for as long as you feel like doing it. It minimizes the chances of procrastination and minimizes stress by taking your emotions into account.
However, like any system, it doesn’t work for everyone. It doesn’t work for me. I find it stressful and counterproductive to switch contexts. I prefer to maintain a flow state for long periods of time because it helps to immerse in a task and understand it better. In fact, recently I’ve discovered that choosing a single thing to focus on for a week can massively increase productivity while keeping your mind calm. It’s like a theme of a week and although there can (and will) be some deviations you always get back to it and concentrate on finishing just one thing. It also helps to prioritize better, because you have only 52 weeks and thus only 52 things to focus on in a year. Of course, for this to work one has to understand the constraints and take no more than he is absolutely sure he can accomplish in a single week.