The Most Important Task idea is refreshingly ruthless: before the day fills with noise, pick the one task that would make the day a success, and do it first. Everything else is negotiable; that one isn't. It works because it sidesteps the trap of a busy day where you tick off ten small things and somehow the thing that mattered never got touched.
The knack is choosing it honestly (the important one, not the easy one) and protecting it from the morning's chaos. This tool lets you set your Most Important Task for the day so it's front and centre, not buried in a list of thirty. Just try it — pick tomorrow's one thing tonight, and do it before the inbox gets its hands on you.