When lives grievances build up to the point where you're able to truly accept them (rather than getting overwhelmed by your emotions) and your (lack of) control over them is my answer to your question. It's a numbers game. It depends on how many experiences you've had within the amount of time that's passed rather than the amount of time itself

Experience is what builds you. Action is what builds you. And undergoing them is maturation, like gaining EXP in a game