To those of you still in your 20s, let me alert you to a day more sickening than that day you found a hair in your diner breakfast. It is the day you turn 30, and your body’s systems and internal mechanics begin their collective campaign toward your painful demise.

It happens very suddenly. And it always strikes in the morning.

You go to bed all fine and dandy, never knowing that you’ve just slept the final sleep of your youth. Because when you awake, your back aches — really aches — really, really aches. It aches so much that you choose to focus your attention on the ever-growing pain in your neck and shoulders.

Soon, that pain becomes so unbearable that your entire body goes into what I have now come to call “morning lockdown.” What lockdown usually means for me is not being able to get out of my bed for some 35 to 45 minutes, sort of like warming up a car on a snowy morning.

In those spiritual moments of morning lockdown, I choose to reminisce over the circus-like wonder of my 20s. I remember being able to eat like an untrained bear, run a mile like a well-trained freak-of-nature shortly afterwards, and still be able to go out drinking that night and not care if a fist-fight broke out as a result of what many would describe as my old Cooper charm.

I also recall pivotal days, like the one when I helped the new athletic director at my college move into her house.

She had a huge leather couch that needed to go up to the second floor and no levers or pulleys to assist the situation. Without a thought, I hoisted the bulky piece of furniture onto my back and lugged it up the stairs with ease, all the while ignoring the strange ripping and burning feeling in my upper back.

The final thought I almost always have during my morning lockdown is a simple one: Pain hurts. I never had that thought in my 20s, but trust me it really does hurt.

If I eat like an untrained bear now, I feel like I have been shot with a tranquilizer. If you see me run a mile now, someone had a revolver to my head.

If I’m about to get punched in the face these days, I simply reply to my attacker, “I’m 30, and I’m not above crying to keep you from hitting me.” And if there is any manual labor involved in my life now, this man shamelessly avoids it.

Take care of yourself in your 20s. Your 30s will not be so kind if you don’t.