The heart of the problem

Gotta get serious for a moment:

In all honesty, I haven't been feeling too well over the past few weeks. It's not that I've been sick, but I've had a general feeling of "blah-ness" for a while. I think it's the dawning realization that I have no idea what to do next with my life. My job's okay- not great, but no complaints either. I'm certainly not bored- I have all kinds of stuff to keep me busy. I just don't feel like I'm doing anything meaningful with my life right now; I'm just working and goofing off. As if on cue, that little voice in the back of our heads tells me "Just hold on. God's got to have something planned for you soon." Problem is that I'm getting antsy and wondering what I should do in the meantime (or if I'm not doing what I should be doing and missing out somehow. Ick.)

Got another little dilemma that'd do some good to bounce off of someone else, instead of being cooped up in my head all the time. I think of my self as a smart kid, and I've probably had far more teaching about God/"spiritual education" than most people in the world. Yet it bugs me to no end that I'm still struggling spiritually. Salvation's easy - it's an academic thing. All you have to do to become saved is to look at all the evidence, understand that it's THE truth, and say "yeah, sure, I believe that Jesus did all that for me." My problem and dawning realization is that it's insanely tougher for me to take that head knowledge and apply it to my stubborn ol' will. What I KNOW I should do, and what I WANT to do really are two seperate things.
How does this "death to self" thing work anyhow? I've tried force of will to do the right thing... and failed miserably after a few days when the novelty or "fire" for God wears off. I've been so guilt-ridden and tired of fighting God that I just submit to whatever, and that works for a few days... until I feel better and slowly begin to slip again. I feel like I'm not growing spiritually at all, and I keep thinking "How is God helping me right now? Am I not broken enough? Do I need a stronger fire for You, God? You say 'I will give you rest,' but then why do I still struggle? I KNOW that I should follow God, but at the same time I very, very often don't WANT to follow God. My mind is set, but my will still fails me." How exactly does God defeat ones sinful nature? What don't I understand yet?

Blah... okay, feeling a little better now.