That means that when people first read the section from Luke that is today's gospel, they knew very well what it meant that Jesus "set his face to go to Jerusalem." They knew exactly what awaited Jesus there. The author of the gospel is reminding them that all the events reported in the coming pages happen against the backdrop of Jesus purposely moving toward Jerusalem and the cross.
I take it from Luke's gospel, the letters of Paul, and much else in the New Testament, that those early Christians struggled as much with the cross as I do. That's especially true in light of Jesus calling us to embrace the way of the cross, even to take up our own.
In today's verses, we learn than a Samaritan village doesn't receive Jesus "because his face was set toward Jerusalem." I'm not 100 percent sure what this means, but I assume that Jesus' focus on Jerusalem and the cross makes them think Jesus won't be doing any neat tricks for them.
I know how they feel. I want Jesus to do stuff for me, and when he's all fixated on the cross, I don't really want to be around him. I don't much care for talk of needing to deny myself, lose myself, take up my cross, and so on.