My son and I share a birthday and every year mom sends us each a Hallmark card.

Getting the card is a reliable thing in an unreliable world. Mom never forgets.

About a decade ago, my son opened his card to find a crisp $20 bill.

He was five at the time and he turned to me with Great Expectations. He wanted to see what my envelope contained. I could see the wheels turning.

It was clear he was thinking that if a child gets $20, the payoff for an adult must be enormous.

I knew even before I opened the card that there would be no crisp Benjamin tucked inside. It would be weird to send me cash. Adults don’t do that.

It’s curious that at some not-clearly defined point we age out of so many things. You stop doing sleepovers, you no longer search for Easter Eggs and you don’t send your adult children cash.

I opened the card and there was a lovely message from my parents.

“What’s inside?” my son asked. “How much money?”

I broke the news that adults don’t get money on their birthdays.

“That’s a rip off!” my son exclaimed.

I told my mom later, and we had a good laugh about how “kids will be kids.”

I reassured her that I appreciated the card and that I hadn’t expected money.

I told her that she and Adam Turkewitz are the only ones I can count on to send me a card every year. (Adam is a banker at Wells Fargo who robo messages me for my birthday and every other holiday.)

My mother sends a birthday card to all her children, grandchildren and some assorted other friends. It’s a lot to keep track of and well above the number for the average American (seven.)

A year later, my son and I got the usual letters in the mail.

My son was delighted to find another brand new $20.

I opened my card and was surprised to find a check.

Mom said she didn’t want to disappoint anyone.

She never does.

(Part of a series of life lessons based on conversations with my parents.)