I feel that one should not spend too much time thinking about this. It's easy for our puny brains to misunderstand this mystery and can lead to various issues. I believe it was St. Francis des Sales who was tempted to despair over it for some time. It's highly disputed regarding how this works, and we'll likely never solve the question. Even the Church refused to rule on it definitively. Especially scrupulous types should avoid this subject entirely.