I might be preaching.

Knowing what's wrong is one thing.
Knowing what's wrong, and what to do to make it right is another thing.
But knowing what's wrong, what to do, and actually doing it is an entirely different struggle.
I'm a Christian.
I'm a Christian, and I have faith in God which is ultimately going to be what saves me, but faith without action is pointless.
I know that there are many aspects of my life that aren't good, not just bad for me physically, but bad for me as a Christian. And I know of quite a few specifics, and I know what I need to do to cut these from my life, but I'm human; I'm a stubborn jackass. I'm scared and my will that used to be so strong isn't anywhere close to what it used to be.
God will forgive me, but again with the ultimately, ultimately it's up to me to take his forgiveness and do something with it.
Life's probably going to suck, and might not be very fun for a while, but nothing NOTHING NOTHING NOTHING on this planet really matters. Everything here is temporary anyways, and unless it's going to make the world a better place, or make people realize how awesome God is, it doesn't matter.
Sure, hanging out with friends, getting wasted, buying really really cool wallets and shirts and stuff, saving up for that amazing house in Northern California is all really fun and cool, but it's nowhere NEAR as cool as all the awesome stuff that's going to be up in Heaven.
It's kind of like saving for retirement. You have to put some stuff aside here and there so that you can have what you need when that times rolls around.