Although we should credit their zeal and enthusiasm, James & John really have no idea what they are asking today. They picture an earthly kingdom where power is for the taking, even if they want to use it for good. Jesus shows them later what true power is. "Right & Left" next mentioned at the cross, in His glory - totally against our expectations, with two criminals at his sides.
Jesus blows our sense of long-term happiness out of the water. We need to keep eternity in perspective.
4 levels of Happiness -
1-Material things and sense-experience
3-Contribution to the common good
4-Eternal things (God Himself)
James & John want low-level happiness: Ego-comparative. They want to build themselves up. They want to pursue the best. They desire great things for themselves. They know there will be some sacrifices but they are ready.
In fact that is most of Americans. Television and magazines prove easily that what we focus on is levels 1 & 2.
1 & 2 are brief & more shallow (doesn't engage our higher spiritual powers).
3 & 4 Long-lasting, deep, and pervasive (not just affecting me).
It might not surprise you that we are stuck in 1 & 2. It might not surprise you that there is a part of all of us that sort of drags us down to those levels, even if we have moved beyond them (concupiscence). But also, God's grace and our cooperation with it will allow us to overcome the gravity of our weakness. And the Lord shows us how in the Eucharist.