Why three?
A long task list answers “what exists?” It does not answer “what matters today?” Today’s Three gives that second question somewhere to live.
You can choose fewer than three. If one difficult thing is the real job of the day, one is enough.
Mix practical and meaningful work
A useful set might contain one commitment, one piece of life admin and one action that moves a goal forward.
Do not automatically fill all three with urgent chores. If every day is only maintenance, your longer-term direction never gets a turn.
When the day changes
Change the three. The feature is meant to reflect reality, not punish you for making a plan before reality arrived.
Nothing is automatically rolled over. Reschedule deliberately so unfinished work does not quietly become tomorrow’s problem.