Today the Jesus of John's Gospel names himself the Good Shepherd, a metaphor with deep roots in the royal theology of the Old Testament. It is an imagination which continues down to our own day; we still talk about pastors and "pastoral" care, and Latin rite bishops and abbots still carry crosiers that resemble the staffs of shepherds.
The first religious house I ever lived in had a pet sheep. They had received her from someone for nothing, so they named her Charity. She didn't have much personality, but earned her stay as a kind of independently contracted lawn-mower. In the morning you could put her in a section of field, and she would alternatively eat grass and sit there all day. Then you could put her somewhere else. Thus Charity helped cut down on the need for lawn care by humans who usually have something better to do.
Being a city kid, I hadn't known any sheep before Charity. My acquaintance with her helped me understand that, though sheep look peaceful and sweet in pictures (especially religious ones), what we see as peacefulness is more accurately termed stupidity. And when you're around sheep, you realize that they don't smell very good.
So imagine yourself as a shepherd, caring for a group of stupid, stinky sheep. Some danger arrives, maybe wolves or robbers or whatever. Do you protect yourself, or do you save the sheep? What if you can't save the sheep without putting yourself in danger? Are you going to put your safety or even your life in jeopardy for a bunch of dumb, smelly sheep?
Of course not. Even if you consider the lives of the sheep to be as intrinsically valuable as your own (and I bet few people would act this way if that's what it came down to), you have an instinct for self-preservation.
Therefore notice how outrageous Jesus' claims are today. He is the Good Shepherd who loves the sheep in a way that goes beyond all reason. He goes so far as to lay down his life for the sheep. Imagine: it's hard enough to contemplate giving up one' s life for a fellow human whom we love, but for some sheep?
Our God is a curious God. This is a God who loves the world so much that he is prepared to let go of of the power, control, and prestige that any reasonable reflection expects of a "supreme being."
This is why it is God himself who is the perfect model of holy poverty. He gives up even what it means to be God in order to enter into the vulnerability which is solidarity with creatures. And through it, even though we kill him over and over in each other, the whole process ends in the great reversal of Resurrection because of the indestructibility of so perfect a love.
When we let go of the good things of the world, that is only the beginning of holy poverty, of living sine proprio, without anything of our own. When we begin to surrender for others what is properly ours by nature, our will, our gifts, our powers, that's when we begin to imitate the God who lays down his life for his sheep.