When your life is going incredibly well. Its as if you get a hard on for your life.
Dude my life is going so well, I have such a raging life boner.
(n)an incredible moment in one's life which elicits the most excellent sensation known to mankind.
Person A:Dude, I just got the largest life boner you could ever imagine!
Person B: What happened?
Person A: I WON THE LOTTERY!!!
Person B: Oh mylanta. You just gave me a life boner, too!