Originally Posted by Joseph
If he's your friend, be there for him for this, and be there for him if it fails. Don't offer advice though unless he asks for it. You can't do a lot for him except anger him if you indicate you are anything but supportive.
I'll chime in on this side of things. Like many have said, you have to be receptive to the message in order to hear it. Otherwise it just creates hard feelings. Your friend isn't receptive and is charging forward. You'll just have to be there for him and pick up the pieces if it happens (or congratulate him on a long and happy marriage, that happens too, marriage is a roll of the dice).
Some people just have to go forward and make the big mistakes in order to learn from them (
). You can warn them all you like, but for many various reasons, they'll think what you are saying is wrong or doesn't apply to them. They have to go on and make a big mistake, pay the price, and suffer for it before it gets embodied into their life code.
I will say that when you learn your lessons this way, it is very painful but you also learn those lessons exceedingly well and learn to never (ever ever ever) go back there again.