Please excuse me for throwing a monkey wrench into this thread. If I'm out of line, please tell me, and I'll not continue to interupt.
This has always confused me, as well. The striking part of this quote is that Jesus says this well before His own crucifixion. I don't doubt that crucifixions were somewhat common in those days. There is much evidence that it was. And Jesus and His disciples were probably exposed to these throughout their lives. Therefore I am not comvinced that to understand this verse we need to hear it in light of what we know about Christ's crucifixion. [But I do believe that he was speaking prophetically.]
With the obvious exception of Jesus, probably the majority of victims of crucifixion were criminals. They were seen with some regularity carrying thier crosses to their deaths.
We all have burdens such as health issues, family problems, economic problems, etc., that are thrust upon us, but I don't think carrying our cross symbolizes these. Those being crucified were carrying the weight and burden of their own crimes and their own sins, those things that they caused in their own lives. I suspect that carrying ones cross has to do more with enduring the burdens and obstacles we have placed in our own way through sin, poor decisions, the consequences of our own actions.
I still do not fully understand this verse, but I feel as if there is a lot more to it than just that Jesus suffered on His way to be crucified, and we should as well, because He said this to his disciples early, before His own crucifixion. But I believe we need to hear this quote putting ourselves in the time and place of those to whom He spoke it.