Many different things.
However some of things that we believe stir up passion only arouse guilt and shame (anyone interested in hearing a sermon on hell, fire and brimstone?).
Personally I find passion in praising and giving thanks in a community.
Last night at a prayer meeting it was good to lift up requests to God in a community, it was even good to visit. But what stirred my heart was when we gave thanks and praised God.
In the circle, for around 10 minutes, there was non-stop praise.
I felt my excitement build as I listened as people thank God for who he is and what he has done.