You start growing up the day nobody else keeps track of your deadlines.

Growing up has a specific switch in it, and the switch is bookkeeping. For years somebody else held the list of what you owed and when, and their reminders did the actual work. The day nobody is holding it, a missed thing stops being a telling off and becomes a consequence. That is the whole transition, and it arrives with no ceremony attached.

Keep the list somewhere outside your head, because memory is the wrong tool for this. One calendar, one place, everything entered the moment you hear about it. It does not need to be clever, only to be the only one.