That sixteen-year-old wouldn't listen to the important things, and would want to hear a bunch about things I think are unimportant now. We'd have serious trouble communicating. Not for lack of wanting to, or because either of us would be rude--I've always been pretty polite--but because he and I wouldn't particularly connect.
Even if we removed the element of paradox--I'm telling this guy things that will change his future, and my past, so that now what I'm telling him is different, so what he does is different, and so forth--there's still the problem of my not wanting to tell him things that he'll learn a lot more from by experiencing first-hand, rather than having me try to hand the experience to him.
For example: the first piece of advice I'd give? "Wear that seat belt. I know it's a pain in the ass in that car you're driving; I've never had a car before or since with such an asinine seat belt-shoulder harness combination, and I've driven a third of a million miles in more cars than I can count since then. This scar on my chin wouldn't be here if I'd worn a seat belt. That crash should have killed you." Even that advice is suspect. He needs to learn that lesson himself, because if he doesn't have that scar to remind him every time he looks in the mirror maybe he blows it off once, at just the wrong time, and gets ejected through the windshield at some other point in that third of a million miles.
And the second piece of advice: "When you listen to other people, do it with more thought to what they're thinking and less to what you're thinking," that just comes with years of experience. It's not something you can just tell someone to do.
"Do the hard stuff first. If you know you can do anything, why start with easy shit?" is something he won't listen to anyway, because he's just as lazy as you are now, and while you now actually do take a crack at the hard stuff first, it's only because you've realized how rewarding it is to succeed at the most difficult tasks before you; it makes everything easy from there. But he'll nod, think it makes a lot of sense, and then go on doing what it was he was doing.
I certainly can't tell him what happened to him was abuse. He'd argue with me all the way, and it'd just make him angry and me sad. It took years of someone who was close enough to me to push all the buttons, and pretty much wear them out mashing them, in order for him to come around on that one. I certainly can't do that in one conversation. And what then? He'd still have to live there, knowing. That's not something I'd inflict on anyone.
Most of the rest? I mean, sure, I can tell him it all works out later: love, travel, friends, money; but at sixteen he was already pretty sure things were going to go fine. (This is the guy who just assumed he was going to get into the college of his choice; talk about blind self-assurance.) In fact, he was a lot more sure about everything than he was a few years later, after he'd fucked up and realized the extent to which he didn't know what he was doing. At sixteen, he thought he had the world figured out to an extent I don't think I do.
It all boils down to experience. And I can't impart that. I haven't been able to do that to people who are a lot more receptive, who've actually came to me and asked. I certainly can't to a guy I'm parachuting in on from the future.
Maybe I'd just give him a lot of investment advice. It's the cliche, and it'd amuse both of us to live out that particular story.