Desiring the Kingdom

We are, at rock bottom, desiring creatures.  We might like to believe we're all very rational, but our center is more in our gut than in our heads.  The question is, what does our heart really desire?  And how did we get that desire?  Jesus's sermon on the mount gives us a challenging picture of a new life -- the good life our heavenly Father wants us to long for.  So, what's our heart's desire?