What is the Heart?

From Tim's sermon on 5/30/2010: 'Self-Control'

Tim's Explanation:

The bible does not divide human beings into head and heart, into faculties like mind and emotions. In fact, if you read the bible carefully, you'll often be confused, because there're many places where it talks about 'thinking from the heart,' and that's because when the bible uses the word heart, it does not mean what we mean in the English language by heart.

The heart was the center of the personality, according to the Bible. And it was the place where your fundamental commitments existed. It's the metaphor for your fundamental trusts and commitments. And, see, what you think and what you feel and what you decide all flow from the heart, because whatever you most trust, whatever you most love, whatever your heart is most passionately trusting and loving in, sets the course for everything else, and if your heart's divided...and you actually don't have one single, over-mastering passion, then your life is going to be out of control, there're going to be all kinds of problems...

My Question: I am increasingly seeing that self-control is my central struggle on a daily basis. Tim's sermon from 5/30 deals with this in great detail, and I'll post about it over the next few days, but I think this portion gets to the heart of the matter: self-control is impossible without one "over-mastering passion."

But is it possible to have that kind of life-ordering passion for God himself? It's must easier for me to find that passion for lesser things.