When your son turns 50, you will remember how, when he was a baby, he would kick the arm of the rocking chair just when you thought he was finally asleep and wake himself up for another 15 minutes of grinning and rocking. And you will smile at the memory.

When your son turns 50, you will remember the endless walks through the neighborhood you took with him rain or shine because your husband had the only car for the family at work. You always visited the little wooden bridge that ran across a tiny stream, and he would jump up and down on it with his hard-soled shoes just to make noise. And you will smile at the memory.

You will remember the evenings that the light on the pole in the backyard next door would throw shadows on the side of your house and you would dance together on the asphalt driveway and laugh at your giant shadows. And you will smile at the memory.

When your son turns 50, you will remember the middle of so many nights when he was a teething toddler, and you would sit at the little folding table with him and eat cheese and crackers at a pretend tea party. And you will smile at the memory.

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When your son turns 50, you will remember being so afraid that he would feel less loved when his new sister or brother was born, and you held him extra tight when you sat in the backyard that summer counting the train cars that passed by and waving at the man in the caboose.

And you will smile because he was such a great big brother, not once but three times, and he sang to them and helped them learn to walk and kick a soccer ball, told them jokes and walked with them on Halloween, and waited to open his Christmas presents so he could watch them open theirs first.

When your son turns 50, you will remember how proud you were of his first-grade report card, and his high school diploma, and then sitting high in the bleachers on the football field crying as your husband sat next to you at his college graduation and wondering where the years had gone.

When your son turns 50, you will remember his wedding day when you hugged him so tight you thought you would hurt him, and he flashed you the most wonderful smile as he walked back up the aisle holding your first daughter-in-law just as tightly. And you will smile at the memory.

You will remember the day his first child was born and the worried look on his face as he stood guard over the tiny bassinet as his jaundiced son lay just beyond his reach even though the doctor told him everything was fine. And you will smile at the memory.

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You will remember proudly walking through the gates of Walt Disney World next to your son even though he was 43, his son was 10, and you were 66 before the dream came true. And you will smile at the sheer magic of that moment, no matter that it was long overdue.

When your son turns 50, you and your husband will secretly fly halfway across the country to attend the surprise party your daughter-in-law throws for him, meet his new closest friends, and watch the video that his friends and family have contributed their best memories of him toward, reinforcing all the wonderful things you always knew about him.

And you will smile at the wonder and the magic and the love your child has brought into your life for 50 years, and at just how quickly those years have passed.

At least, that’s how it happened to me when our son turned 50.