I have started using a paper notebook for an agenda/planner/to-do-list thing. It's been an interesting experiment. I notice that I tend to waste all kinds of time configuring whatever computer program I use, but there is no such thing as that with the paper notebook, because “configuring” it and using it are one: both of these consist in writing lines, symbols, and characters with the pen on the page. You create the scaffolding the same way you create the content. This is not so with computer-based tools because, while writing prose on a computer is very easy – a computer even has special hardware designed for it – organizing that prose visually – as one wants to do when one is making an agenda (a section of the page for each day of the week, for example) – is vastly more cumbersome. Some computer-based task-management or calendar-management tools are actually very good – but they cost at least as much as my notebook did, and I have more confidence that my notebook will be useful to me, for a long time and in a variety of contexts, than any piece of software.