This is a good one. I'm just through the transition to fatherhood, so I don't see 5 years from now being terribly different than now, except that my kids will be older and there will be more than one of them. But I can give it a shot.
First off, be patient - remember how you learned patience in 2010 and keep applying that. Your kids will try you but don't let them get to you. You have a great depth of patience and understanding that you didn't even know you had and just started to discover in 2010.
2nd, Drive - keep up your drive, don't settle too far into a routine, don't let yourself get complacent about your career or your life. It's easy to get stuck in the routine and not push and challenge yourself, but don't let yourself get to that point. You don't want to be in a situation where you have career issues.
Those are the two main things I can think of. This is a tough one, because it's hard to envision what I'll be like in 5 years.
If I wrote a letter to myself of 10 years ago, here's what it would sound like:
Dear 2000 Bill,
The next 10 years will bring you great adventures in your life. That woman you just met and started dating? She'll end up being your wife and the mother of her child. Treat her right. Do all the little things for her - she'll appreciate it.
The things you find important now, you won't in 10 years, and your friends will come and go. Don't get too caught up in the dramas of the day, a lot of that will seem silly later on. Only dedicate time to those in your life that show an interest in reciprocating. Don't spend too much time on friendships where it doesn't seem like there is a strong mutual interest, you'll only get burned by that.
You will grow in ways you didn't even expect over the next 10 years. Enjoy the Ride.
Sincerly, 2010 Bill