E/O Challenge: Nail (100 words exactly)

This popped into my head about 4 o'clock this morning and it's been bugging me ever since. Hope it makes sense!

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A Lesson Learned

The nail, embedded deep in the dusty floorboard, would be a challenge to extract he realized as he tried to gain purchase on the rusty metal.

As he worked patiently at the splintered wood he thought about his future self; about the cold, unfeeling man he was destined to become.

He remembered the bitter words, the un-emotional revelation that Sammy was dead and he wasn't with him when it had happened.

By the time, with fingers bloodied, he pulled the nail free Dean already knew he'd learnt his lesson - it just wasn't the one Zac had wanted to teach.