Why do we say "just"?
We use the word just to emphasize that we are talking about a small part, not the whole amount. Like, "I'm just having a bite." It's a little bit, or a short amount of time, as when a person says, "I'm just going to the store" or "I made it just in time." St. Joseph probably thought of himself as just Joseph - a regular guy called to a really important mission.

The big paradox
I remember a time when I was in a print shop, and the person behind the counter asked me, "Was this done by a graphic designer?" I answered, "No. It was done by me. I'm just a girl." I still think of myself that way. Lately, however, God has been showing me that in order to use me for his purposes, he needs me to see the ways in which he has made me more than just a girl. True humility means seeing ourselves as we truly are.

God is infinite, and in comparison to him we recognize our own finitude, our smallness, our being less than. At the same time, created in the image and likeness of God, we have the capacity to accomplish beyond our human capability, with the aid of God's grace.

This paradox, of being seemingly nothing and yet everything, is at the heart of the Incarnation, which we celebrate on Christmas Day. God's coming as one of us elevates our human condition to the divine; we are at once helpless and at the same time powerful. We are sinners, and saints in the making. We are broken and whole, dead and alive, worthless and worthy. The unimaginable is in our reach, with God's grace.

Joseph was a Just Man
Joseph was a just man because he lived a virtuous live. By looking to St. Joseph, we can see that growing in virtue is the way to becoming just. This is an important learning for us, because we, too, have the ability to be just! It's what God wants for us. God needs us to move beyond thinking we are just ourselves, in order that he can use us for His BIG purposes - like he used Joseph.