When Peter rebuked Jesus for saying "that the Son of Man must undergo great suffering, and be rejected by the elders, the chief priests, and the scribes, and be killed, and after three days rise again" he was expressing a very common understanding of the Messiah, one that he had learned. Unlearning things like that is often the work of a lifetime. All of us have ideas about life that we have learned, and some of these ideas need to be unlearned.
In writing about the call of Abraham in the Letter to the Romans, Paul characterizes Abraham's body as being "as good as dead." How often do we think of the older members of our communities as being no longer capable of contributing anything of value? Is that an idea about older people that we need to unlearn?
It seems that it took Peter a long time to unlearn his ideas about the Messiah, but he needed the shock of Jesus' rebuke - "Get behind me, Satan! For you are setting your mind not on divine things but on human things." - to jumpstart the unlearning. Perhaps Lent can be a time when I let God jumpstart the unlearning that I need to do in my life.