Read Watchmen. Get depressed, then learn how to apply it to life.
I gave you the meaning of life in 3 fucking steps, right there.
Actually, no, I'LL SPILL THE FUCKING BEANS RIGHT NOW. (and no more shitty references to the Hitchhiker's Guide, dear fuck)
It's whatever the fuck you want it to be, kiddo. The meaning of life can be to jerk off all over frigging printed out pictures of your favorite Japanese anime. It can be to worship Cthulu. It can be to rip your dick off and telepathically learn to control it. The world's a blank fucking page. That's it. Morals are shit. The whole good and evil thing- shit. I mean, if you want to put it in logical terms, there's a really fucking insignificant chance the ENTIRE HUMAN RACE, let alone you, will make an impact on the universe. All of these conceited notions after we as animals, came up with after staring at this blank fucking slate for too long, are shit. We don't live to live, we just fucking exist, living our meaningless lives until we die.
So come up with your own meaning, dickface. "Rational" or not.