I kept a to-do list for eleven years, in roughly nine systems. Paper, then an app, then a different app, then a text file, then back to paper, then the app with the good keyboard shortcuts. I stopped about two years ago and have not gone back.
What went wrong with it
The list was never a list of what I was going to do. It was a list of everything I had ever felt guilty about not doing, sorted by how recently I had felt guilty. Adding to it was frictionless; removing something without doing it felt like a small moral failure. So it grew.
By the end I had a hundred and forty open items and I was doing about four things a day, none of which were on the list, because the actual work of a given day is obvious and does not need writing down.
What replaced it
A calendar and an index card. The calendar holds anything with a date and a consequence — deadlines, calls, the tax filing. The index card holds today, in pen, three items maximum, written in the morning and thrown out at night.
The throwing out is the mechanism. Nothing carries over automatically. If a thing matters, I will write it again tomorrow, and if I write it four days running without doing it, that is information — usually that I do not actually intend to do it, and should say so to whoever is waiting.
The obvious objection
Things get dropped. Yes. Small things, mostly, and the world has absorbed it. I have forgotten to reply to two people in two years and both forgave me. Against that: I have not opened a productivity app in twenty-four months, and I no longer carry around the low hum of a hundred and forty unfinished obligations.