You have a huge store of pithy and useful encapsulations of faith in your head–such as
“Body, Blood, Soul, and Divinity”–which show up almost as an involuntary response when needed.
For instance, when you hear the question: Why did God make you?
this is the exact first answer that pops into your mind:
“God made me to know Him, to love Him, and to serve Him in this world,
and to be happy with Him for ever in heaven.”
Oh, and you know the capital sins, the spiritual works of mercy, the corporal works of mercy…
And you don’t need a bulletin to remind you what the Holy Days of Obligation are. You do need the bulletin to keep the times straight when the obligation has been abrogated in your diocese, but it doesn’t matter, because you’re going to Mass, anyway.