I have been tracking ToDos for years now. The tool I've finally settled on is TickTick, as it provides the necessary features - ability to prioritize tasks, schedule tasks for dates, set recurring tasks, organize tasks into lists, which in turn can be categorised into categories.... What I have tried (and failed) though is putting all important tasks on the calendar. While it works for those that don't have an external dependency, but it fails for those that do. For example, if an important task on my list requires me to talk to another person, what if they're not available at the time? What if they need 2 days to get back? It can become a whole lot of calendar management if you tracked everything on the calendar.