Lifelong Best Friend's Fundamental Changes Making Friendship Difficult

Yo gooseman,
I've got a good buddy that I grew up with. Back in the day he was straight as a string, went to church, didn't drink, didn't even cuss. About 10 years ago I noticed he got to picking up some bad habits. He started drinking and smoking dope. I still like to hang out with him but all he wants to do is go party and chase skirts. I'm not down with that stuff, maybe the skirt chasing but not the partying.  What do I do?  I don't want to just write him off but I'm afraid I might have to.

Dear Best Friends For (awhile),
The only constant in this world is change, climate change, gender change, spare change, tire change--you see where I'm going here. Think of people as sediment in the path of water, picture a stream of water compassing a stone, a larger, stronger current splits as it hits the rock and heads left, the smaller, weaker current goes left. The rock will eventually move, which direction will it go?  If you love your buddy, influence him in the right direction, the stronger your influence the more likely he is to be moved your direction. Keep in mind that oftentimes there are unseen influences just under the surface that might impede the rock or your buddy from going your direction. Keep this in mind as well, the rock also influences the water, your buddy might end up changing you!  It's your life, your buddy, do the best you can and keep on flowing, you might just have to float on down and find some more rocks.  I should have been a philosopher, I made every bit of that up--pretty proud of myself!
​-MG