This is a great point. It's easy when you're young and strong to ignore the 'health and safety' lectures in workplaces about lifting with your knees and not your back, dividing loads, things like that. It can feel silly and un-natural when you're young and feel invinsible, and lifting heavy boxes doesn't hurt you at all. But it's still doing minor damage that builds up, and as someone who did a lot of heavy lifting work when I was in my teens and early twenties, but is now in her late thirties, believe me, you'll wish you'd followed those health and safety pointers when the pain begins.
My mother has been disabled from her back problems for decades now, even a major surgery inserting rods and pins into her spine didn't do enough to repair the damage and ease the pain. You don't want to make a mistake in your teens and twenties that ends up with decades of pain.
Back problems are awful and very hard to fix, so be safe! You're smart enough to take care of yourself, just please be careful now, so you'll still be strong and able later on in life
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