How Mick Foley is not only alive and well, but speaks and writes intelligently is a complete mystery to me. He's taken more physical punishment to his head and every other part of his body than pretty much anyone else.
Foley wasn't really known as a drug user though. So staying away from that probably helped him. I am surprised he didn't get hooked on pain pills or something though
It was gruesome seeing Foley get nailed with 10 unprotected chair shots to the head (while handcuffed) in that infamous I Quit match against The Rock in '99 at the Royal Rumble. Just like you, I am amazed at his functioning in daily life since then, 17 years later, without many reported issues.